Hello Faustian Bargain (interesting monicker by the way);
On the subject of parts upgrades, you might try a higher quality headphone jack if it's a 1/4" jack - Neutrik makes some nice ones. However, I know of no 1/8" jacks that are of particularly high quality.
Yes, older electrolytic condensors are certainly fair game for replacement. So are some other types, which can become somewhat soggy due to moisture absorbance over the years.
Depending on localised heating, some of the carbon comp resistors may have drifted rather a ways from their nominal values. This is easily determined with a VOM or DMM.
You might also check the various grounding points for signs of corrosion - it doesn't take much to foul up a ground shackle and introduce some hum into the mix.
As far as speakers are concerned, be aware that many of the older small diametre fullrange drivers are actually quite fine little numbers! For one thing, you are likely to find an alnico magnet lurking in there, which would cost an arm and a leg today - if you could even find one of the right size. I'd leave it as is unless there was some reason to replace it (i.e. it's damaged). If the driver is damaged beyond repair, then Tang Band and Fostex both make some very nice little 3" and 4" fullrange drivers.
Good luck with your radio!!
All the best,
Morse
On the subject of parts upgrades, you might try a higher quality headphone jack if it's a 1/4" jack - Neutrik makes some nice ones. However, I know of no 1/8" jacks that are of particularly high quality.
Yes, older electrolytic condensors are certainly fair game for replacement. So are some other types, which can become somewhat soggy due to moisture absorbance over the years.
Depending on localised heating, some of the carbon comp resistors may have drifted rather a ways from their nominal values. This is easily determined with a VOM or DMM.
You might also check the various grounding points for signs of corrosion - it doesn't take much to foul up a ground shackle and introduce some hum into the mix.
As far as speakers are concerned, be aware that many of the older small diametre fullrange drivers are actually quite fine little numbers! For one thing, you are likely to find an alnico magnet lurking in there, which would cost an arm and a leg today - if you could even find one of the right size. I'd leave it as is unless there was some reason to replace it (i.e. it's damaged). If the driver is damaged beyond repair, then Tang Band and Fostex both make some very nice little 3" and 4" fullrange drivers.
Good luck with your radio!!
All the best,
Morse
As to alterations/improvements it depends on how much you want to spend I suppose...
Remember that the set was designed with the capabilities/limitations of the components of the time in mind, so if you decide to make alterations with modern components it may not give you the results you expect without making circuit changes elsewhere in the set. So, for example, if you were to replace the speaker for a more modern full range unit, or replace the output tranny for a better unit, this might just show up limitations in the audio amp or cause instability unless the feedback arrangements are also seen to.
As far as the RF side is concerned, if you can borrow a signal generator for aligning the RF and IF circuits this is probably all you need to do to get optimum results. Aim to get a smooth symmetrical response from the IF circuits.
Remember that the set was designed with the capabilities/limitations of the components of the time in mind, so if you decide to make alterations with modern components it may not give you the results you expect without making circuit changes elsewhere in the set. So, for example, if you were to replace the speaker for a more modern full range unit, or replace the output tranny for a better unit, this might just show up limitations in the audio amp or cause instability unless the feedback arrangements are also seen to.
As far as the RF side is concerned, if you can borrow a signal generator for aligning the RF and IF circuits this is probably all you need to do to get optimum results. Aim to get a smooth symmetrical response from the IF circuits.
dhaen said:It's beautifully uglyLooks about 1957 to me.
Unforunately, it's very difficult to buy stuff like this in the UK now, except for at specialist sales.
In the last few years the safety legislation has been tightened, and anything sold, must conform by testing.
It costs to get the stuff tested, and much of it fails, so it tends to all get junked.
in the East Coast U.S. audio nuts grab this stuff at estate sales all the time, but if you go to the Midwest or Florida (Florida is where most people from the U.S. go to die) you'll find a lot ! There was great stuff at the Goodwill Store in Melbourne Florida -- home of Harris Semiconductor and just up the road from Cape Canaveral -- seems that everyone who worked there pocketed test equipment or wrench sets., etc.
At some point EBay will be so glutted with stuff from Salvation Army and Goodwill stores that the prices will reflect reality.
It's still possible to pick up stuff cheaply here on occasion, despite the laws on electrical safety. We get weekend markets called car boot sales around the country - not sure if you get them in the States although they appear elsewhere in Europe. Last week I got a nice little AM/FM tube set in a moulded cabinet at one of these sales for £10 (about $15-$16). My best bargain this year at one of these sales has been a 30 watt guitar amp with EL34 pp outputs for £5 (about $8). It was in good working order too!
thanks for the replies
well, there is currently no 'jack in the box', so to speak. so i'd have to add one myself. one idea is to wire an external little box (with a selector switch), so as not to deface the original chassis.
my question here is a really dumb one: how do i wire a stereo jack to a mono source?
-----as for the speaker, i probably won't touch it. i do have a spare RS 40-1197 4-incher, which might work if necessary.
/andrew
Morse said:
well, there is currently no 'jack in the box', so to speak. so i'd have to add one myself. one idea is to wire an external little box (with a selector switch), so as not to deface the original chassis.
my question here is a really dumb one: how do i wire a stereo jack to a mono source?
-----as for the speaker, i probably won't touch it. i do have a spare RS 40-1197 4-incher, which might work if necessary.
/andrew
faustian bargin said:
Your jack will have a common connection (-) for both channels and you connect the two (+) together, to allow your mono signal to feed two stereo headphone channels. I assume that you are going to take the signal from the speaker connections in the set - without knowing the model is it an AC or AC/DC set, does it have a mains transformer? With an AC/DC set there are safety considerations to taken into account...
DO NOT attempt to wire a headphone jack into this radio! The output, whiuc is USUALLY isolated by teh output transformer, is NOT isolated in this set, as a negative feedback circuit is used. You'd have to add your own isolation transformer to make it safe.
On ther other hand, it has two speakers, including an electrostatic tweeter, so you may find it sounds pretty good.
On ther other hand, it has two speakers, including an electrostatic tweeter, so you may find it sounds pretty good.
Tom Bavis said:
When replacing a selinium rectifier with a silicon one, the series resistor value needs to be adjusted. Unless it smells, leave the selinium rec in place as a solder point, with just one end disconnected.
If you need to repace the main smoothing "can", you can hollow-out the old one, and fit individual replacement caps inside.
The hum from these AC/DC sets is typically higher than we'd expect now days, so don't expect too much.
Please heed Tom's earlier warning about the live speaker connections.
Cheers,
thanks for the great suggestions
yes, adding a headphone out is no longer a consideration, until i'm ready to figure out the isolation transformer.
so...the smoothing cap: in the schematic, is it the 3-lead one? labeled C38A, B, & C, at 40, 60, and 80 microF's respectively. can i use 3 separate caps, or do i need to use a triple lead to replace it?
also, the specs say the resistors are typically 10% tolerance carbon, and the caps are typically 20%...should i attempt to use components that more closely match the designed values? there are actually some resistors that are called out at 20% - why was that? were they less critical and therefore cheaper?
yes, adding a headphone out is no longer a consideration, until i'm ready to figure out the isolation transformer.
so...the smoothing cap: in the schematic, is it the 3-lead one? labeled C38A, B, & C, at 40, 60, and 80 microF's respectively. can i use 3 separate caps, or do i need to use a triple lead to replace it?
also, the specs say the resistors are typically 10% tolerance carbon, and the caps are typically 20%...should i attempt to use components that more closely match the designed values? there are actually some resistors that are called out at 20% - why was that? were they less critical and therefore cheaper?
re-capping tips
i found a neat 'tips' page for beginners like me. it's a commercial site so no flames, but the info is good. they sell capacitors, schematics, etc....they will even assemble a 'capacitor kit' for a particular make/model of radio. (no i'm not associated with them, i just thought it was an interesting service.)
Just Radios - capacitor tips
one tip/warning i didn't realize: if your radio hums, it's best not to let it play until you've replaced the filter caps, as that can be hard on the tubes.
also i learned the 'multisection' filter caps were originally used to save space and cost.
i found a neat 'tips' page for beginners like me. it's a commercial site so no flames, but the info is good. they sell capacitors, schematics, etc....they will even assemble a 'capacitor kit' for a particular make/model of radio. (no i'm not associated with them, i just thought it was an interesting service.)
Just Radios - capacitor tips
one tip/warning i didn't realize: if your radio hums, it's best not to let it play until you've replaced the filter caps, as that can be hard on the tubes.
also i learned the 'multisection' filter caps were originally used to save space and cost.
ok, so i have on order some capacitors to re-cap the radio. good job, me.
now, i'm wondering if someone can clue me in on replacing the rectifier/resistor combo. i don't know how to go about determining which silicon rectifier replacement i need. there aren't any values written by the 'SE1' symbol, so I assume it should be easy for the experienced eye to tell just by looking at the surrounding schematic. I can sortof sense what I'm supposed to be looking for (i.e. wattage rating), but I'm not sure what else I'm missing.
***
dear moderator - if you feel i have totally hijacked this thread please do not hesitate to make a new one...i originally felt i was contributing to the 'thrift store' theme, but now it seems i'm running my own project here.
***
/andrew - is not a hijacker, but he plays one on TV.
now, i'm wondering if someone can clue me in on replacing the rectifier/resistor combo. i don't know how to go about determining which silicon rectifier replacement i need. there aren't any values written by the 'SE1' symbol, so I assume it should be easy for the experienced eye to tell just by looking at the surrounding schematic. I can sortof sense what I'm supposed to be looking for (i.e. wattage rating), but I'm not sure what else I'm missing.
***
dear moderator - if you feel i have totally hijacked this thread please do not hesitate to make a new one...i originally felt i was contributing to the 'thrift store' theme, but now it seems i'm running my own project here.
***
/andrew - is not a hijacker, but he plays one on TV.
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