Greetings from a newbie,
I have a question concerning rebuilding a pair of Heathkit W-5M's that I recently purchased. One amp sounds very good - neat and clean assembly but still has the original caps. The other amp is a mess - all the parts are there but the only thing keeping a number of them from falling out is the bottom plate. This amp needs to be taken apart and re-assembled. It looks like a very unskilled monkey did the soldering.
Now for the question - I have the layout and parts list for a power supply capacitor board that replaces the 2 large can capacitors and most of the large axial caps. I also have an AudioXpress article that details amp/power supply updates using parts available from Antique Electronic Supply - this just replaces existing parts with a few minor upgrades.
This is brand new territory for me. I sure there are pros and cons for each approach. Advice/opinions are needed and welcome.
Kevin, aka firenewt
I have a question concerning rebuilding a pair of Heathkit W-5M's that I recently purchased. One amp sounds very good - neat and clean assembly but still has the original caps. The other amp is a mess - all the parts are there but the only thing keeping a number of them from falling out is the bottom plate. This amp needs to be taken apart and re-assembled. It looks like a very unskilled monkey did the soldering.
Now for the question - I have the layout and parts list for a power supply capacitor board that replaces the 2 large can capacitors and most of the large axial caps. I also have an AudioXpress article that details amp/power supply updates using parts available from Antique Electronic Supply - this just replaces existing parts with a few minor upgrades.
This is brand new territory for me. I sure there are pros and cons for each approach. Advice/opinions are needed and welcome.
Kevin, aka firenewt
Hi Kevin,
Since you claim to be new at this, here is what I recommend. Repair the bad amp back to normal using the good amp as a model standard. Don't be concerned about updating this and modifying that just yet. Get it working correctly and see how you like it. Listen to it as it originally was. They were pretty good amps to begin with. Once you're familiar with them, then you can consider making changes and modifications. My 2¢
Victor
Since you claim to be new at this, here is what I recommend. Repair the bad amp back to normal using the good amp as a model standard. Don't be concerned about updating this and modifying that just yet. Get it working correctly and see how you like it. Listen to it as it originally was. They were pretty good amps to begin with. Once you're familiar with them, then you can consider making changes and modifications. My 2¢
Victor
Hi Victor,
That's a really good idea. I have a tendency to jump in the deep end and then check if I can swim. I am retired (not by choice) so I have plenty of time on my hands. Besides it will be a good learning experience.
I became interested in tubes about a year ago after being a solid state kind of guy for the last 35 years. I purchased and assembled the S-5 Electronics stereo amp - assembled, not built since all it took was soldering components to a board. A small simple amp but that was all it took to make me rethink my ways.
Since then I've picked up a Heathkit AA-141 preamp and a AMC CVT 2030 power amp. Didn't take much to get them working - listening to them as I type.
You will no doubt see many more questions from me, BUT only after I search previous postings.
Kevin
That's a really good idea. I have a tendency to jump in the deep end and then check if I can swim. I am retired (not by choice) so I have plenty of time on my hands. Besides it will be a good learning experience.
I became interested in tubes about a year ago after being a solid state kind of guy for the last 35 years. I purchased and assembled the S-5 Electronics stereo amp - assembled, not built since all it took was soldering components to a board. A small simple amp but that was all it took to make me rethink my ways.
Since then I've picked up a Heathkit AA-141 preamp and a AMC CVT 2030 power amp. Didn't take much to get them working - listening to them as I type.
You will no doubt see many more questions from me, BUT only after I search previous postings.
Kevin
Hi Kevin,
I totally agree with Victor, but if you mean that you have built solid state amps for the last 35 years you are not new to building techniques and what goes on. If that is the case you might as well check the electrolytics at the outset. They must be quite old (if originals) and if you are comfortable with it you might invest in new ones from the outset. (I presume you are aware of safety measures for high voltage!)
You might also consider (now or later) replacing the 5U4 rectifier tube with a 5AR4/GZ34 (direct replacement) with advantage. It generates less heat and has the advantage of a slow turn-on, avoiding high peak d.c.voltages on the power supply capacitors. This is not so much a "design change"; the GZ was simply not around when this design came out.
It so happened that I was asked the same question just a week ago by a local friend, making my first aquaintance with the W-5M. Perhaps the mentioned article is the one also showing an under-chassis picture, which will further enable you to trace if anything has been changed also in your working amplifier. One of the pictures will also show how original components were changed for more modern ones in a rather neater layout - that for later then. This is a version of the classic Williamson amplifier and well worth having. (Many of us cut our teeth on that design.)
Best wishes!
I totally agree with Victor, but if you mean that you have built solid state amps for the last 35 years you are not new to building techniques and what goes on. If that is the case you might as well check the electrolytics at the outset. They must be quite old (if originals) and if you are comfortable with it you might invest in new ones from the outset. (I presume you are aware of safety measures for high voltage!)
You might also consider (now or later) replacing the 5U4 rectifier tube with a 5AR4/GZ34 (direct replacement) with advantage. It generates less heat and has the advantage of a slow turn-on, avoiding high peak d.c.voltages on the power supply capacitors. This is not so much a "design change"; the GZ was simply not around when this design came out.
It so happened that I was asked the same question just a week ago by a local friend, making my first aquaintance with the W-5M. Perhaps the mentioned article is the one also showing an under-chassis picture, which will further enable you to trace if anything has been changed also in your working amplifier. One of the pictures will also show how original components were changed for more modern ones in a rather neater layout - that for later then. This is a version of the classic Williamson amplifier and well worth having. (Many of us cut our teeth on that design.)
Best wishes!
Hi Johan,
Never built a solid state amp from scratch but have put together a number of amps using available modules, boards etc. I also have had the "pleasure" of diagnosing and repairing some. Matter of fact, I have a pair of Sony ES home theater amps awaiting some attention. Picked them up at an auction - got them cheap. Don't think I will be working on them for awhile - not near as much fun as tubes. I got a copy the Heathkit W-5M assembly manual in the mail today so I'll not flying blind.
Kevin
Never built a solid state amp from scratch but have put together a number of amps using available modules, boards etc. I also have had the "pleasure" of diagnosing and repairing some. Matter of fact, I have a pair of Sony ES home theater amps awaiting some attention. Picked them up at an auction - got them cheap. Don't think I will be working on them for awhile - not near as much fun as tubes. I got a copy the Heathkit W-5M assembly manual in the mail today so I'll not flying blind.
Kevin
Kevin,
My suggestion would be to CAREFULLY take the bad amp apart and completely rebuild it (my first suggestion was going to be to get the manual but you already thought of that!). If it's as big of a mess as you indicated, this could give you a few advantages:
1. You could check the value of each of the parts against the parts list. Carbon composition resistors have a nasty habbit of changing value when they get this old. Measure with a decent DMM. Remember, you only have to be within the tollerance of the original value.
2. You could eliminate some wiring errors all at one time. If parts are actually falling off, it may have been worked on several times and the quality of workmanship sounds iffy at best. It also sounds like you can solder better than whoever built the amp, so you would eliminate a lot of potential bad solder joints.
3. After you have disconnected all of the parts, you could unmount the transformers and choke and perhaps give them a fresh coat of paint. It's amazing what a can of Rustoleum spray paint can do for the look of a ratty transformer! You could also wash the bare chassis and get off years of dirt.
4. And last but not least, you will have the fun of building a complete Heathkit! Many other kit manufacturers came close to matching Heath's throughness in assembly instructions but no one was ever really as good as Heath.
Your idea of replacing the electrolytic capacitors to start with might not be a bad one. When they get this old, they can either just stop working or give you some exciting pops and bangs when you power it up.
Good luck and keep us posted. It is great to see folks reviving these old amps instead of just throwing them away.
Ken
My suggestion would be to CAREFULLY take the bad amp apart and completely rebuild it (my first suggestion was going to be to get the manual but you already thought of that!). If it's as big of a mess as you indicated, this could give you a few advantages:
1. You could check the value of each of the parts against the parts list. Carbon composition resistors have a nasty habbit of changing value when they get this old. Measure with a decent DMM. Remember, you only have to be within the tollerance of the original value.
2. You could eliminate some wiring errors all at one time. If parts are actually falling off, it may have been worked on several times and the quality of workmanship sounds iffy at best. It also sounds like you can solder better than whoever built the amp, so you would eliminate a lot of potential bad solder joints.
3. After you have disconnected all of the parts, you could unmount the transformers and choke and perhaps give them a fresh coat of paint. It's amazing what a can of Rustoleum spray paint can do for the look of a ratty transformer! You could also wash the bare chassis and get off years of dirt.
4. And last but not least, you will have the fun of building a complete Heathkit! Many other kit manufacturers came close to matching Heath's throughness in assembly instructions but no one was ever really as good as Heath.
Your idea of replacing the electrolytic capacitors to start with might not be a bad one. When they get this old, they can either just stop working or give you some exciting pops and bangs when you power it up.
Good luck and keep us posted. It is great to see folks reviving these old amps instead of just throwing them away.
Ken
Ken,
The amp is really as bad as I stated. I'll take a picture of it before I start the disassembly. I remember back in the early sixties a good friend of my dad got a pair of the W-5M's. I thought they were the coolest things. My amps are in good physical condition - no rust on the transformers or choke. The paint isn't bad either. Only down side is one of the cages has been drilled and 5-way posts and a headphone jack added. I am pretty good with a soldering iron and can read schematics with the help of my cheat sheets. Also found an online resistor calculator - just plug in the colors and presto, the value is displayed.
I have some questions/concerns regarding replacement parts.
1. I have a bunch of NOS carbon resistors. From what I have read here, a carbon resistor tends to drift with age. Also, from what I can tell there is a number of camps as far as which resistor type is best. - carbon, carbon film, metal film etc. I'm thinking at this point of using carbon film or metal film. Which ever I use will eventially be used in the other amp. Opinion?
2. I have a lot of NOS Sprague Atom caps. They test good on my cap analyzer so is there any reason not to use them? Again, whatever I use will ultimately be used in the other amp. Opinion?
I think I will start the controlled destruction tonight - can't wait.
Regards,
Kevin
The amp is really as bad as I stated. I'll take a picture of it before I start the disassembly. I remember back in the early sixties a good friend of my dad got a pair of the W-5M's. I thought they were the coolest things. My amps are in good physical condition - no rust on the transformers or choke. The paint isn't bad either. Only down side is one of the cages has been drilled and 5-way posts and a headphone jack added. I am pretty good with a soldering iron and can read schematics with the help of my cheat sheets. Also found an online resistor calculator - just plug in the colors and presto, the value is displayed.
I have some questions/concerns regarding replacement parts.
1. I have a bunch of NOS carbon resistors. From what I have read here, a carbon resistor tends to drift with age. Also, from what I can tell there is a number of camps as far as which resistor type is best. - carbon, carbon film, metal film etc. I'm thinking at this point of using carbon film or metal film. Which ever I use will eventially be used in the other amp. Opinion?
2. I have a lot of NOS Sprague Atom caps. They test good on my cap analyzer so is there any reason not to use them? Again, whatever I use will ultimately be used in the other amp. Opinion?
I think I will start the controlled destruction tonight - can't wait.
Regards,
Kevin
Hey Kevin,
Regarding resistors and capacitors:
The discussions about these componets has raged on for many years with as many opinions as there are brands of amplifiers, resistors and capacitors combined. Add to this plenty of dogma spread around by advertising hype and extreme viewed writers. There are a few guide lines that you can use, but in short, your ears will have to be the judge of what is best for you.
In fourty plus years of being an audiofiend (I mean phile...heh-heh) I've had my share of discussions on the sound of things and what is and isn't best. When someone claims that old carbon resistors and paper capacitors are bad and should be upgraded, I always ask them this. Why do so many audiophiles roll their eyes and swoon over the sound of those marvelous old Mercury Living Presence and RCA Living Stereo shaded dog recordings when they were made with electronics that were infested with those very same parts?
I don't think I've ever gotten a satisfactory answer to that. And it isn't just microphone placement. And why are Sprague Vitamin-Q capacitors so coveted and sought after? They're just paper and oil in a hermetically sealed can. Check out the price of NOS Allan-Bradley carbon resistors on eBay. Unbelievable! Albeit they are the best of the carbon comps.
Truth be known, all resistors are subject to drift with use. With wire wounds being least affected. Some characteristics to consider are that carbon composition resistors will withstand an overload without burning out quickly. For this reason alone, they would seem to compliment tubes. Film resistors can't take an overload and were designed for RF and higher frequency circuits do to their surface resistance. Of course they can be used for audio too, and where you need close tolerance for RIAA values.
Plastic dielectric capacitors (I'm using that term broadly) may give you a little more frequency extention if you have the output transformer (or ears) to hear it. But they are not always a good thing. In the case of a circuit that has any equalization designed in using paper capacitors, the response will be altered if plastic capacitors of the same value are substituted.
Remember, audio amplifiers are not compelex devices like some RF and microwave circuits that require the ultimate in stability from componets. Some folks will apply RF practices to audio where it serves no real advantage forgetting that audio is the bottom basement of the spectrum.
I would say to use what you've got to start with. Then experiment with different type later.
Victor
Regarding resistors and capacitors:
The discussions about these componets has raged on for many years with as many opinions as there are brands of amplifiers, resistors and capacitors combined. Add to this plenty of dogma spread around by advertising hype and extreme viewed writers. There are a few guide lines that you can use, but in short, your ears will have to be the judge of what is best for you.
In fourty plus years of being an audiofiend (I mean phile...heh-heh) I've had my share of discussions on the sound of things and what is and isn't best. When someone claims that old carbon resistors and paper capacitors are bad and should be upgraded, I always ask them this. Why do so many audiophiles roll their eyes and swoon over the sound of those marvelous old Mercury Living Presence and RCA Living Stereo shaded dog recordings when they were made with electronics that were infested with those very same parts?
I don't think I've ever gotten a satisfactory answer to that. And it isn't just microphone placement. And why are Sprague Vitamin-Q capacitors so coveted and sought after? They're just paper and oil in a hermetically sealed can. Check out the price of NOS Allan-Bradley carbon resistors on eBay. Unbelievable! Albeit they are the best of the carbon comps.
Truth be known, all resistors are subject to drift with use. With wire wounds being least affected. Some characteristics to consider are that carbon composition resistors will withstand an overload without burning out quickly. For this reason alone, they would seem to compliment tubes. Film resistors can't take an overload and were designed for RF and higher frequency circuits do to their surface resistance. Of course they can be used for audio too, and where you need close tolerance for RIAA values.
Plastic dielectric capacitors (I'm using that term broadly) may give you a little more frequency extention if you have the output transformer (or ears) to hear it. But they are not always a good thing. In the case of a circuit that has any equalization designed in using paper capacitors, the response will be altered if plastic capacitors of the same value are substituted.
Remember, audio amplifiers are not compelex devices like some RF and microwave circuits that require the ultimate in stability from componets. Some folks will apply RF practices to audio where it serves no real advantage forgetting that audio is the bottom basement of the spectrum.
I would say to use what you've got to start with. Then experiment with different type later.
Victor
Well, those parts werent old when they were new. They hadnt had 40+ years to absorb water, become leaky, and drift. Whether they were good in the first place is another question. Water is the bane of PIO caps, some PIOs are hermetically sealed because of this.
Using a generously speced (thermalwise) resistor should reduce drift, whatever the type.
Some recommend mildly baking resistors (of some types) to force thier drift, then measuring them for use.
Hello Tweeker,
To say that fourty year old parts drift and become leaky will get no argument from me. They sure do. Especially those old "bumble bee" capacitors with the stripes. (more on that below)
However, Kevin was asking about using using new old stock parts verses brand new modern parts. And it was in that context and mindset that I was responding. Certainly one would not use fourty year parts to rebuild an amplifier. (or would they?) With the exception of electrolytic caps, resistors and most capacitors age very little on the shelf. This is assuming they were kept in a good environment and physically undamaged. So it was a question of how much better were the newer style verses the old.
Agreed.
To bake resistors to force them to drift is something I have no experience with. I've never tried it. I tend to think it would have more to do with current flow over time then outside temperature. But not being a manufacturer, I have no intimate knowledge of their compounds and behavior.
Bumble bee capacitors. I never cease to be amazed at the price some people will pay for these old dogs. Even obviously used ones that, by their age, are surley leaky. Search eBay's completed items for "bumble bee cap*" and you'll see what I mean. Here's an example" Unbelievable!
http://cgi.ebay.com/Sprague-022mfd-...69QQihZ017QQcategoryZ7266QQrdZ1QQcmdZViewItem
Victor
To say that fourty year old parts drift and become leaky will get no argument from me. They sure do. Especially those old "bumble bee" capacitors with the stripes. (more on that below)
However, Kevin was asking about using using new old stock parts verses brand new modern parts. And it was in that context and mindset that I was responding. Certainly one would not use fourty year parts to rebuild an amplifier. (or would they?) With the exception of electrolytic caps, resistors and most capacitors age very little on the shelf. This is assuming they were kept in a good environment and physically undamaged. So it was a question of how much better were the newer style verses the old.
Agreed.
To bake resistors to force them to drift is something I have no experience with. I've never tried it. I tend to think it would have more to do with current flow over time then outside temperature. But not being a manufacturer, I have no intimate knowledge of their compounds and behavior.
Bumble bee capacitors. I never cease to be amazed at the price some people will pay for these old dogs. Even obviously used ones that, by their age, are surley leaky. Search eBay's completed items for "bumble bee cap*" and you'll see what I mean. Here's an example" Unbelievable!
http://cgi.ebay.com/Sprague-022mfd-...69QQihZ017QQcategoryZ7266QQrdZ1QQcmdZViewItem
Victor
Ah, I see. NOS carbon comps should be as fine as they ever will be, its usually thermal cycling that causes drift.
If your cap tester can test leakage and ESR and says they are fine, they are probably fine, though unsealed NOS PIO could readily go bad on a musty warehouse shelf.
Baking resistors was a trick Morgan Jones cited in Valve Amplifiers for aging wireound resistors. It worked by relieving tension in the wires. Jones tested by throwing all his alu clad ww resistor in the oven at minimum temperature for a day, then letting them slowly cool in oven. Resistors greater than 4 years old showed no change in value, whereas new ones would change ~1/2% and not change much further. This isnt something Id try with carbon comps.
If your cap tester can test leakage and ESR and says they are fine, they are probably fine, though unsealed NOS PIO could readily go bad on a musty warehouse shelf.
Baking resistors was a trick Morgan Jones cited in Valve Amplifiers for aging wireound resistors. It worked by relieving tension in the wires. Jones tested by throwing all his alu clad ww resistor in the oven at minimum temperature for a day, then letting them slowly cool in oven. Resistors greater than 4 years old showed no change in value, whereas new ones would change ~1/2% and not change much further. This isnt something Id try with carbon comps.
As to what resistor type is best, this depends in part on the resistors value and role. Some types are unsuited for some roles, such as wirewounds make poor grid stoppers, due to inductance. Inductance in wireounds ceases to be much issue in most circuits past 10K ohms R, and here they have noise advantages over any other type.
Guys,
I think there might have been a little misunderstanding about the advice I was giving Kevin on the parts. I was merely suggesting he check the value of each of the parts he removes from the bad amp and replace anything which is out of tolerance. This should get the amp working as Heath designed it, which, I believe should be the first goal. He can have his case of audiophilia nervousa later!
The important thing with coupling caps, other than being sort of close to the value specified, is leakage at the voltage in the circuit. I have many older capacitors which actually test good for value and dissipation on my battery-operated hand-held LCR meter but leak like a screen door when I test them on my old Heathkit capacitor checker. The Heath tests leakage at the rated working voltage of the cap. As said, the black turkeys with the stripes are usually the worst.
Kevin, in case you're wondering why all this discussion, if a coupling cap passes a little DC along with the AC, it changes the intended bias on the next stage. This changes the operating point of that part of the circuit and usually leads to all kind of strange behavior. If it is the coupling cap to an output tube, it usually leads to "orange plate disease".
Victor, not to be argumentative, but my junk box disagrees with your assertion that carbon composition resistors don't change with age. I have many old resistors which, when measured with a good DMM, are way high in value, many times even above the next value in the 10% series (is that E24?). Some of these I know I bought new in the 1960s and were probably only used once for a short while in a project. They are probably Allen Bradley or Ohmite, since that is what Allied Radio was selling at the time if I remember correctly. Now I measure every carbon comp resistor I pull out of the drawer and only use the ones which are at least within their marked tolerance. The rest hit the trash can I keep under the bench. Maybe I could make a fortune selling them on FleaBay!! 
I think there might have been a little misunderstanding about the advice I was giving Kevin on the parts. I was merely suggesting he check the value of each of the parts he removes from the bad amp and replace anything which is out of tolerance. This should get the amp working as Heath designed it, which, I believe should be the first goal. He can have his case of audiophilia nervousa later!
The important thing with coupling caps, other than being sort of close to the value specified, is leakage at the voltage in the circuit. I have many older capacitors which actually test good for value and dissipation on my battery-operated hand-held LCR meter but leak like a screen door when I test them on my old Heathkit capacitor checker. The Heath tests leakage at the rated working voltage of the cap. As said, the black turkeys with the stripes are usually the worst.
Kevin, in case you're wondering why all this discussion, if a coupling cap passes a little DC along with the AC, it changes the intended bias on the next stage. This changes the operating point of that part of the circuit and usually leads to all kind of strange behavior. If it is the coupling cap to an output tube, it usually leads to "orange plate disease".
Victor, not to be argumentative, but my junk box disagrees with your assertion that carbon composition resistors don't change with age. I have many old resistors which, when measured with a good DMM, are way high in value, many times even above the next value in the 10% series (is that E24?). Some of these I know I bought new in the 1960s and were probably only used once for a short while in a project. They are probably Allen Bradley or Ohmite, since that is what Allied Radio was selling at the time if I remember correctly. Now I measure every carbon comp resistor I pull out of the drawer and only use the ones which are at least within their marked tolerance. The rest hit the trash can I keep under the bench. Maybe I could make a fortune selling them on FleaBay!!
A few years ago - one of the best pair of Heath W-5s I heard was a pair rebuilt by a local tube guru - it had a battery bias front end, fixed bias mod, wirewounds for the plates on the input tubes... running old EL37s - it had a fast dynamic sound.
A good restoration will improve the sound, but you may want to consider doing some well placed modifications.
A good restoration will improve the sound, but you may want to consider doing some well placed modifications.
I have thousands upon thousands of NOS carbon comp resistors gathered from various "estate" sales through the years. 1/4 watt through 2 watt. Some are fancy Allen-Bradleys; some are no-name. Most of them have drifted somewhat, either to the edge of the tolerance band or outside of it, in many cases far outside the band, just sitting on the shelf for decades. And these are truly NOS.
Geeze, I've thrown buckets of these things out. had I known...
Also a little experience gathered over a few decades.
I cannot qualify as to make and cost, but many resistors I found in QuadIIs that I refurbished aged upward by up to 30%. Also, the Quad 22 control unit (but also other makes) used capacitors resembling "styrene" types (I could never find exactly what they were) that had values of 2 - 3 times the nominal! (This would be over some 30 - 40 years.)
If baking resulted in only 0,5% change, I would certainly not loose sleep. One must remember that components also have a temperature co-efficient; they would probably change by more than that over the temperature range experienced under-chassis in practice.
The space-age has certainly resulted in component reliability improving by orders of magnitude. I cannot imagine that anyone would prefer old carbon resistors (or new) to present-day metal film or metal oxide types (the latter can stand somewhat higher temperature extremes). That is not making "40 year ago" components bad, it is simply materials development. In audio it seems a little over-the-top imo to go much beyond the quality of metal film resistors and polyester capacitors for normal applications. This is not r.f., much though some awed folks would like to weave an aura of mysticism here.
Regards
I cannot qualify as to make and cost, but many resistors I found in QuadIIs that I refurbished aged upward by up to 30%. Also, the Quad 22 control unit (but also other makes) used capacitors resembling "styrene" types (I could never find exactly what they were) that had values of 2 - 3 times the nominal! (This would be over some 30 - 40 years.)
If baking resulted in only 0,5% change, I would certainly not loose sleep. One must remember that components also have a temperature co-efficient; they would probably change by more than that over the temperature range experienced under-chassis in practice.
The space-age has certainly resulted in component reliability improving by orders of magnitude. I cannot imagine that anyone would prefer old carbon resistors (or new) to present-day metal film or metal oxide types (the latter can stand somewhat higher temperature extremes). That is not making "40 year ago" components bad, it is simply materials development. In audio it seems a little over-the-top imo to go much beyond the quality of metal film resistors and polyester capacitors for normal applications. This is not r.f., much though some awed folks would like to weave an aura of mysticism here.
Regards
Hi wa4htz & Brian,
I'm sorry to read that you guys have large reject rates of your NOS resistors. My comments were based mostly on my personal experiences. I too have thousands of unused older stock carbon resistors. Almost all of them are Allen-Bradley because they are what I've always prefered. And most of them are still in sealed flat packages of 25 or 50 pieces each, except what I keep handy in a couple small dispenser cabinets.
I measure them before use as you do, but have not found that many out of tolerance. Sure there were some as would be expected. Perhaps a nominal 5% or so. But I think that's acceptable. Remember, they were never 100% tested at the factory. Only batch checked.
Being in the used equipment business, I do have good digital meters from Hewlett-Packard, Keithley and others in my shop. Still I'm at a loss to explain your OOT numbers. Perhaps I have not checked enough of my own to get the full picture. Or they may not be as old as yours. Don't know. But I'm from the old school, and it was always generally accepted knowledge that good resistors had a long shelf life.
For basic capacitor testing I use a Sencor LC-75 digital tester. This has up to 600 volts DC for both leakage and ESR as well as a ring test for inductors. Something I once only did with my scope. I also have an old Heathkit condenser tester. I think it's a CT-3. My parants gave it to me as a gift many years ago when I was young. It still works fine and I turn it on every so often to keep it happy. I will never-ever part with it.
Johan said:
Did you read my earlier comment regarding overloads with a carbon comp verses film?
Another reason would be in keeping an amplifier original when restoring it. In much the same idea that one would restore a classic car. You wouldn't want air bags or tinted windows in a model T Ford would you?
Also, Kevin asked about using the NOS resistors that he had on hand. Assuming they are not OOT, they should work fine. I honestly feel that for a basic power amplifier like this, new metal films won't buy you anything. You might sleep better at night knowing they're in there, but I doubt if you'll hear much, if any, difference. Not just by doing that.
Yo Tweeker,
BTW, that book "Valve Amplifiers" by Morgan Jones sounds interesting. I'll probably try getting a copy soon. Thanks for mentioning it.
Victor
I'm sorry to read that you guys have large reject rates of your NOS resistors. My comments were based mostly on my personal experiences. I too have thousands of unused older stock carbon resistors. Almost all of them are Allen-Bradley because they are what I've always prefered. And most of them are still in sealed flat packages of 25 or 50 pieces each, except what I keep handy in a couple small dispenser cabinets.
I measure them before use as you do, but have not found that many out of tolerance. Sure there were some as would be expected. Perhaps a nominal 5% or so. But I think that's acceptable. Remember, they were never 100% tested at the factory. Only batch checked.
Being in the used equipment business, I do have good digital meters from Hewlett-Packard, Keithley and others in my shop. Still I'm at a loss to explain your OOT numbers. Perhaps I have not checked enough of my own to get the full picture. Or they may not be as old as yours. Don't know. But I'm from the old school, and it was always generally accepted knowledge that good resistors had a long shelf life.
For basic capacitor testing I use a Sencor LC-75 digital tester. This has up to 600 volts DC for both leakage and ESR as well as a ring test for inductors. Something I once only did with my scope. I also have an old Heathkit condenser tester. I think it's a CT-3. My parants gave it to me as a gift many years ago when I was young. It still works fine and I turn it on every so often to keep it happy. I will never-ever part with it.
Johan said:
Did you read my earlier comment regarding overloads with a carbon comp verses film?
Another reason would be in keeping an amplifier original when restoring it. In much the same idea that one would restore a classic car. You wouldn't want air bags or tinted windows in a model T Ford would you?
Also, Kevin asked about using the NOS resistors that he had on hand. Assuming they are not OOT, they should work fine. I honestly feel that for a basic power amplifier like this, new metal films won't buy you anything. You might sleep better at night knowing they're in there, but I doubt if you'll hear much, if any, difference. Not just by doing that.
Yo Tweeker,
BTW, that book "Valve Amplifiers" by Morgan Jones sounds interesting. I'll probably try getting a copy soon. Thanks for mentioning it.
Victor
Hi Victor,
Yes, I did read your earlier post and agreed mostly. Perhaps I overstated here. I would certainly agree that as far as keeping appearances right, use carbons! There is not much wrong with them. What I really meant (and should have stated more clearly), was that apart from appearances, components 50 years hence have undergone development. (In all fairness, this is not like adding air bags to a vintage car; it is simply like making the same component from perhaps a better grade of steel than 50 years ago where it needed replacement.)
I also have a few Mercury Living Presence records! I would agree with Tweeker; those components were not old then.
In fact (I might make a few enemys) I don't really agree with this perceived "dramatic" differences in sound between carbon and new resistors - not in audio. Qualitive statements are often misleading; there are also other reasons for a perceived change in quality, not least of which is this that our ears are simply not this mighty super-consistent device some make them out to be. (Again agreeing with you: Differences are often pointed out that will only exist in r.f., not as low as audio.)
No, my thoughts were merely about stability over future decades. What you say about overload is also entirely true, but then also, should not the rating be conservative anyway? (I cannot imagine putting 5W resistors everywhere just in case something might overload - and I have cooked a few resistors in my time! - mostly my stupidity.)
On capacitors, well ...... my ears are not good enough to hear small differences anymore (if I ever did), so I go with measurements - call it second best if you wish. A few years ago in a series of articles on capacitors by Cyril Bateman, very extensive tests showed differences in harmonic product generation between older paper-in-oil and e.g. polyester (although both were quite good); also with other types of capacitor.
So I was not in "opposition" to you in any aspect - apology if that impression was generated.
Regards.
Yes, I did read your earlier post and agreed mostly. Perhaps I overstated here. I would certainly agree that as far as keeping appearances right, use carbons! There is not much wrong with them. What I really meant (and should have stated more clearly), was that apart from appearances, components 50 years hence have undergone development. (In all fairness, this is not like adding air bags to a vintage car; it is simply like making the same component from perhaps a better grade of steel than 50 years ago where it needed replacement.)
I also have a few Mercury Living Presence records! I would agree with Tweeker; those components were not old then.
In fact (I might make a few enemys) I don't really agree with this perceived "dramatic" differences in sound between carbon and new resistors - not in audio. Qualitive statements are often misleading; there are also other reasons for a perceived change in quality, not least of which is this that our ears are simply not this mighty super-consistent device some make them out to be. (Again agreeing with you: Differences are often pointed out that will only exist in r.f., not as low as audio.)
No, my thoughts were merely about stability over future decades. What you say about overload is also entirely true, but then also, should not the rating be conservative anyway? (I cannot imagine putting 5W resistors everywhere just in case something might overload - and I have cooked a few resistors in my time! - mostly my stupidity.)
On capacitors, well ...... my ears are not good enough to hear small differences anymore (if I ever did), so I go with measurements - call it second best if you wish. A few years ago in a series of articles on capacitors by Cyril Bateman, very extensive tests showed differences in harmonic product generation between older paper-in-oil and e.g. polyester (although both were quite good); also with other types of capacitor.
So I was not in "opposition" to you in any aspect - apology if that impression was generated.
Regards.
Greetings,
First off, I'd like to thank everyone for the advice given. The amount of information on this site and the willingness of members to help is greatly appreciated.
To Tweeker - When I first constructed my foil hat, I grounded it to the lightning rod ground. Haven't been the same since the first thunderstorm.
Scrapped that idea - lined my workroom with foil instead.
Back to the original topic: The deconstruction is now complete. Too bad scrap solder doesn't have any value. I found 2 caps and a few resistors that were not on the schematics - I gave up trying to determine their purpose. Component leads were simply stacked one on top of another. Blob of solder on top of blob of solder. Some of the solder wouldn't melt no matter how high I set my iron - plumbers solder maybe?
I've decided to completely strip it and rebuild from the ground up. I figure the next week will be taken up by finding/testing parts and going over the assembly manual and schematics.
This is going to be fun!
Kevin
First off, I'd like to thank everyone for the advice given. The amount of information on this site and the willingness of members to help is greatly appreciated.
To Tweeker - When I first constructed my foil hat, I grounded it to the lightning rod ground. Haven't been the same since the first thunderstorm.
Scrapped that idea - lined my workroom with foil instead. Back to the original topic: The deconstruction is now complete. Too bad scrap solder doesn't have any value. I found 2 caps and a few resistors that were not on the schematics - I gave up trying to determine their purpose. Component leads were simply stacked one on top of another. Blob of solder on top of blob of solder. Some of the solder wouldn't melt no matter how high I set my iron - plumbers solder maybe?
I've decided to completely strip it and rebuild from the ground up. I figure the next week will be taken up by finding/testing parts and going over the assembly manual and schematics.
This is going to be fun!
Kevin
Kevin ...ooooh, very late from me.
Poor solder joints after several decades! How I occasionally suffered with those. It would appear that there is some high melting point solder on your amplifier - then beware! There might even have been soldering fluid
used.
I became the victim of oxide creeping in under ostensible good joints. When I simply resoldered there was still no good contact. If in doubt clean off all solder (suck, wick, whatever) and inspect the surface, and scrape clean if in doubt. You would probably know that only if you see the solder flow you have a proper joint. Same goes for leads of old components.
Apology if this is unnecessary advice, but rather that than frustration. It is not uncommon to find this situation on old equipment.
Regards.
Poor solder joints after several decades! How I occasionally suffered with those. It would appear that there is some high melting point solder on your amplifier - then beware! There might even have been soldering fluid
used.I became the victim of oxide creeping in under ostensible good joints. When I simply resoldered there was still no good contact. If in doubt clean off all solder (suck, wick, whatever) and inspect the surface, and scrape clean if in doubt. You would probably know that only if you see the solder flow you have a proper joint. Same goes for leads of old components.
Apology if this is unnecessary advice, but rather that than frustration. It is not uncommon to find this situation on old equipment.
Regards.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.