See this thread:http://www.diyaudio.com/forums/solid-state/167580-output-capacitor-subjective-objective-views.html
I tried to buy 3300 uf 100v non-polar capacitors, received 3300 uf 100v capacitors with a plus on one end. So CDE saved money on ink by not printing the "DC" Anyway, I hooked up 4 of them to make a 3300 uf cap, 2 back to back and then 2 more to make up the 1/2 in series rule. I put them on the output of a CS800s amp which uses relays, current transformers & a microprocessor for protection. It sounded funny on top octave steinway piano compared to no caps. Also it sounded worse than my Steinway console sitting between the speakers. Without the series caps the SP2-XT speakers sound pretty good. Bass & midrange were fine. I reserve judgement on how actual non-polar electrolytics sound, I haven't bought any. I've tried to find 3300 uf film caps, the cheapest I can find involve paralleling 66 each 50 uf 600 VAC genelec caps at $15 each, or $990 per channel. I'm not going to do that.
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Hi Ian, There are thermo switches on the heatsink['s but thats maybe what switched the crowbar on. As the fan slowed or stopped,the heat would have risen, output would have sagged a little (Mosfets) the volume would have been punched up, then the crowbar....?
Caps are a good idea if I can find a couple thousand MFd at 150v. Why 11,000 Mfd the switch on thump must have been audible around the neighborhood.....
Nearly all the amplifiers I built many years ago were single rail and used output coupling caps...remember the Sinclair series? Eventually I modified some of those for split rail and used bigger devices etc.....I could have lost a few speakers then. Sinclairs were great smoke generators...I spent a lot of money on smoke!
Caps are a good idea if I can find a couple thousand MFd at 150v. Why 11,000 Mfd the switch on thump must have been audible around the neighborhood.....
Nearly all the amplifiers I built many years ago were single rail and used output coupling caps...remember the Sinclair series? Eventually I modified some of those for split rail and used bigger devices etc.....I could have lost a few speakers then. Sinclairs were great smoke generators...I spent a lot of money on smoke!
IndianJoe, I thought that normal caps would be OK. I always used polarised devices and never had any serious problems. Ideally maybe polarised would be better but not discharging and charging through or into each other in that format.....I reckon they would be fighting against each other and that's where the distortion would have come from.
Yes, the dynakit ST120 is single rail, has 3300 polar output caps, and with the bias mod and faster O.T. mod, sounds good. The output cap stays at 45-55 VDC. Split rail amps make an output cap go through 0v where chemical events happen. My experiment with the split supply CS800s proves those chemical events are audible, at least on back to back polar electrolytics. That is why I am building a 3 channel ST120 copy for my organ to replace the tube amp with bad sockets, instead of a more "respectable" split supply amp. I bought the PV1.3k for the organ but it would toast the speakers if it went out of control; it will be repaired & sold off.
The ST120 (1966 design) was bought toasted in 1984 & after repair got so hot it melted the solder on the output cap once. (3.5 hour choir rehearsal). Closed feedback bias circuit (djoffe mod) helps control thermal runaway, and I installed PCAT fans to control the melting the solder problem.
The ST120 (1966 design) was bought toasted in 1984 & after repair got so hot it melted the solder on the output cap once. (3.5 hour choir rehearsal). Closed feedback bias circuit (djoffe mod) helps control thermal runaway, and I installed PCAT fans to control the melting the solder problem.
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Ah yes of course....what I have forgotten...the obvious stuff, yes you would need a bipolar device.
I have a tonewheel Hammond that I haven't even started yet...well I replaced the slides.....I have a spare amp board, but when I get it working I may put in a different amplifier....Mine has a Yamaha 'lesley' uni. I think the LDRs need replacement..very soft!
I have a tonewheel Hammond that I haven't even started yet...well I replaced the slides.....I have a spare amp board, but when I get it working I may put in a different amplifier....Mine has a Yamaha 'lesley' uni. I think the LDRs need replacement..very soft!
That was an interesting and busy thread, Indianajo. It seemed everyone dropped in and we had some fun. Caps are sure "polarizers"
That cap was no bipolar, I looked closely at it and shifted it in and out of circuit, checking the tab labels. Here in Oz at the time, we made mostly high quality motor control and lighting caps which are suited to AC punishment. I figured this may have been its origin. Still, with the benefit of hindsight, I might similarly suggest a couple of 6,800 uF back to back electros, paralled by a single 3-5 uF film cap and equal "bleeder" like resistors across each electro. to centre any DC or the signal. Obviously, the voltage rating needs to be adequate for the rails as a big popped electrolytic makes a helluva mess and your ears ring for days.
Relays: Good luck locating DC rail voltage rated relays. To avoid welded contacts, that's what will be needed to break arcs ($$$$)
Fans: Well, reliability is the name of the pro audio game and the sensing methods vary from bimetal switches to Micro controller integrated multi point control systems. OEMs use different ideas but they can all be fooled to some extent or simply fail. Just stacking against a wall or trash blocking already fluffed up vents can still be disastrous. They still need overtemp power cutouts to back up fans.
A little reading on safety systems might be a good idea between bursts of activity. Ben Duncan and Randy Slone put a lot of emphasis on big amps and their needs - perhaps not always big enough but there is more useful info there than other books on amps. Slone's book is in print and cheap over the net and Duncan's is quite old now but I have the text on another PC courtesy of a DIYAudio member.
That cap was no bipolar, I looked closely at it and shifted it in and out of circuit, checking the tab labels. Here in Oz at the time, we made mostly high quality motor control and lighting caps which are suited to AC punishment. I figured this may have been its origin. Still, with the benefit of hindsight, I might similarly suggest a couple of 6,800 uF back to back electros, paralled by a single 3-5 uF film cap and equal "bleeder" like resistors across each electro. to centre any DC or the signal. Obviously, the voltage rating needs to be adequate for the rails as a big popped electrolytic makes a helluva mess and your ears ring for days.
Relays: Good luck locating DC rail voltage rated relays. To avoid welded contacts, that's what will be needed to break arcs ($$$$)
Fans: Well, reliability is the name of the pro audio game and the sensing methods vary from bimetal switches to Micro controller integrated multi point control systems. OEMs use different ideas but they can all be fooled to some extent or simply fail. Just stacking against a wall or trash blocking already fluffed up vents can still be disastrous. They still need overtemp power cutouts to back up fans.
A little reading on safety systems might be a good idea between bursts of activity. Ben Duncan and Randy Slone put a lot of emphasis on big amps and their needs - perhaps not always big enough but there is more useful info there than other books on amps. Slone's book is in print and cheap over the net and Duncan's is quite old now but I have the text on another PC courtesy of a DIYAudio member.
Its working! Both channels. No parts needed apart from fuses. I will reassemble it and give it a kick in the ribs to see, but should be good. Its working on +-40v rails and seems good.
I had the fan problem which is fixed, then some dissolved tracks...corrosion under the solder mask. That black copper is a dead giveaway. Lets hope +- 100v rails will be OK but I will do that tomorrow. Thanks for the input chaps.
I had the fan problem which is fixed, then some dissolved tracks...corrosion under the solder mask. That black copper is a dead giveaway. Lets hope +- 100v rails will be OK but I will do that tomorrow. Thanks for the input chaps.
Great that it's functional.
The oxidised copper tracks suggest heat over a long time and undersize tracks, since the Mosfets will just keep powering up to their dissipation plateau. 'Odd that wasn't accounted for in the design except for temperatures in S.E. Queensland being a fair bit warmer than the UK!
That must be an awful job to tackle. What have you had to do to repair it so far?
The oxidised copper tracks suggest heat over a long time and undersize tracks, since the Mosfets will just keep powering up to their dissipation plateau. 'Odd that wasn't accounted for in the design except for temperatures in S.E. Queensland being a fair bit warmer than the UK!
That must be an awful job to tackle. What have you had to do to repair it so far?
Yes, here on the coast I have come across a lot of this. it seems that parts of the solder mask are porous or have pin holes due to oil or grease during application....may be fingerprints at the edges. this results in moisture penetrating trough to the copper and corrosion resulting. Seen a lot of electronic organs crippled through corroded tracks and all I needed to do was buzz them out and patch.
I picked up a Yamaha Sound field processor a few years ago, not working, and just repaired some tracks to fix it.
So far I have fixed the fan, but wonder if it is only meant to come on when the heatsink starts to get hot...now its on all the time. I did replace a w/w resistor and about 12 fuses. This amp has no current limiting resistors in the Drain or Source lines. Just the little gate resistors and of course they are OK.
Rule No1 in fault finding....Check voltages.
Rule No2 Have a good look!
Rule No3 signal paths, I use a xtal earpiece and capacitor to do the first check by ear through the signal path and often pick up faults really quickly!
This thing really jumps even on 40% supply!
This unit was built in the US but unable to find the factory...maybe dead! cheers
I picked up a Yamaha Sound field processor a few years ago, not working, and just repaired some tracks to fix it.
So far I have fixed the fan, but wonder if it is only meant to come on when the heatsink starts to get hot...now its on all the time. I did replace a w/w resistor and about 12 fuses. This amp has no current limiting resistors in the Drain or Source lines. Just the little gate resistors and of course they are OK.
Rule No1 in fault finding....Check voltages.
Rule No2 Have a good look!
Rule No3 signal paths, I use a xtal earpiece and capacitor to do the first check by ear through the signal path and often pick up faults really quickly!
This thing really jumps even on 40% supply!
This unit was built in the US but unable to find the factory...maybe dead! cheers
Hi
Interesting - the earpiece I haven't heard of on power amps before.!
If there is a controller, logic says the fan should be at or return to lowest status (off) after switch on from cold. 'Don't know the system, but if it's bimetal button switches on the sink, give them a test for NO or NC status at least. Control circuits and sensors.. well...now you'll have to wing it!
Interesting - the earpiece I haven't heard of on power amps before.!
If there is a controller, logic says the fan should be at or return to lowest status (off) after switch on from cold. 'Don't know the system, but if it's bimetal button switches on the sink, give them a test for NO or NC status at least. Control circuits and sensors.. well...now you'll have to wing it!
Wonderful device with a 2 mfd capacitor and a probe. One 'earth' clip and away you go. Amazing what you can learn about amplifiers when you can listen in.
I used one for ages fixing electronic organs...absolutely indispensable!
Almost better than a scope...probably much quicker! You know roughly what should be there and if it ain't you will find out why not.
I used one for ages fixing electronic organs...absolutely indispensable!
Almost better than a scope...probably much quicker! You know roughly what should be there and if it ain't you will find out why not.
Obviously, 2,000 kpF
I think mfd would be widely recognized as an abbreviated, not a systematic term for microfarad dating back to before any of us were born. Translator software would have a problem, just as with most of our masses of achronyms and jargon. Since millifarad is a recent term, its always written 'mF' and no more confusable than 'MF', if you think about it. The rest Andrew, are...
I think mfd would be widely recognized as an abbreviated, not a systematic term for microfarad dating back to before any of us were born. Translator software would have a problem, just as with most of our masses of achronyms and jargon. Since millifarad is a recent term, its always written 'mF' and no more confusable than 'MF', if you think about it. The rest Andrew, are...
Obviously, 2,000 kpF
dating back to before any of us were born.
Speak for yourself Ian, some of us have one foot in the grave!
Hi Nico
Only one foot? I count my age but not talent with Carlos, Lineup and Hugh. We should all look in the mirror as little as possible.
Well, to get some perspective, I have a DVD archive of our original electronics magazine from 1939 to its modernisation to "Electronics Australia" in 1965. It predates Wireless World with beginnings as a weekly in 1922. The terms used borrow from US and UK articles and journals in the postwar years, so I'm implying it's not just local usage.
Now, Doug Self has taken to archiving Wireless World articles on amplifiers from 1950 until copywright prevents him, so take a look at the top left corner items.
The Douglas Self Site. It should be amusing to see the travesties we once thought acceptable terms.
Only one foot? I count my age but not talent with Carlos, Lineup and Hugh. We should all look in the mirror as little as possible.
Well, to get some perspective, I have a DVD archive of our original electronics magazine from 1939 to its modernisation to "Electronics Australia" in 1965. It predates Wireless World with beginnings as a weekly in 1922. The terms used borrow from US and UK articles and journals in the postwar years, so I'm implying it's not just local usage.
Now, Doug Self has taken to archiving Wireless World articles on amplifiers from 1950 until copywright prevents him, so take a look at the top left corner items.
The Douglas Self Site. It should be amusing to see the travesties we once thought acceptable terms.
really, Andrew, millifarad is an impossibility for any gear built before 1980? If it is millifarad, it is big enough to print all the zeroes of microfarad on it. My huge objection is to assuming u is a micro. If you have done any physics, u and micro are different characters. I have about 1000 kilograms of electronic gear around here and every capacitor is marked in mf , pf, color dots, or color bands. If it is new enough to have millifarad on it, it is probably not broken, or too cheesily built with SMD's and multi-layer PCB's to be repairable.
Does the amp work yet at 90v rails? I've just put the heater in series with mine, am trying to work up the nerve to turn it on and see what else is broken besides the melted PCB traces I just spliced. I had 5 a car fuses in the + base drive to the O.T.'s, instead it burnt a speaker return trace again. Have installed 5 a car fuses in the speaker return line from the O.T. subassy, watch it burn the - base drive line this time (no jumpers to run through a fuse). It burnt the leads off both .5 w zeners I put on the base drive lines to clamp them below 3.3v off speaker return, am trying 3.6V 1w zener base drive clamps this time to blow the fuse before all the driver semiconductors go (again).
Well, I did it. It is amazing how the trouble light doesn't blink with 80 ohm in series with the transformer. Rails are still +- 80, no dc out the speaker terminal !
Does the amp work yet at 90v rails? I've just put the heater in series with mine, am trying to work up the nerve to turn it on and see what else is broken besides the melted PCB traces I just spliced. I had 5 a car fuses in the + base drive to the O.T.'s, instead it burnt a speaker return trace again. Have installed 5 a car fuses in the speaker return line from the O.T. subassy, watch it burn the - base drive line this time (no jumpers to run through a fuse). It burnt the leads off both .5 w zeners I put on the base drive lines to clamp them below 3.3v off speaker return, am trying 3.6V 1w zener base drive clamps this time to blow the fuse before all the driver semiconductors go (again).
Well, I did it. It is amazing how the trouble light doesn't blink with 80 ohm in series with the transformer. Rails are still +- 80, no dc out the speaker terminal !
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Ha Ha Ha, 'mfd' is the notation used before the 60s to denote microfarads. I only use it because I have not got a 'micro' key and have to go into drop downs to insert the symbol....pain.
Old Dubalier 'condensers' from the Australian valve radios of the 40s like AWA, Healing used them........But its not important what the value is, 2, 10....even 0.1 will do, just to hear a signal.
Sorry for the confusion.
Old Dubalier 'condensers' from the Australian valve radios of the 40s like AWA, Healing used them........But its not important what the value is, 2, 10....even 0.1 will do, just to hear a signal.
Sorry for the confusion.
I'm old enough to remember what 'Body, end, dot' means. When men were men, and women were double breasted. Before 8 tracks or 4 tracks, before transistors, before stereo, before color TV, before plastic, before fibre-glass, before sliced bread. I was innoculated for smallpox and polio when I was a kid and cars had steel dash boards, with no seat belts or air bags, no radial tyres and had to stop with only drum brakes and a prayer!
A Baby boomer...we even invented Rock and Roll!
A Baby boomer...we even invented Rock and Roll!
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