Old thread, but renewed several times, i give it try!
Ive got, what a assume to be echocord s62, all markings was gone, the unit was in a terrible condition.
After a electrolytic capacitor replacement it came alive. Full tube change (5xecc83, 1x ecc82) The preamp section works fine.
But theres no echo. I have installed to new tape loops and checked the switches and pots.
The transformer (choke) DCN601 does not seem to work. I cannot measure any electricity on the 126/65 v side.
I´m a absolute beginner in this, so i might got it all wrong. As i read the diagram
http://www.peel.dk/Dynacord/pdf/Echocord Super 62 full service manual (76-103).pdf
There should be two wires out, one to LF4 with 65 volts, and one 127v to the am4 four heads.
I can't measure any impedance between the sides on the dcn601.
Does my troubleshooting seem right? Could i confirm my theory in any other way?
And, where cold i find a suitably transformer if its kaputt? 280 v dc in, 65/127 out?
Ive got, what a assume to be echocord s62, all markings was gone, the unit was in a terrible condition.
After a electrolytic capacitor replacement it came alive. Full tube change (5xecc83, 1x ecc82) The preamp section works fine.
But theres no echo. I have installed to new tape loops and checked the switches and pots.
The transformer (choke) DCN601 does not seem to work. I cannot measure any electricity on the 126/65 v side.
I´m a absolute beginner in this, so i might got it all wrong. As i read the diagram
http://www.peel.dk/Dynacord/pdf/Echocord Super 62 full service manual (76-103).pdf
There should be two wires out, one to LF4 with 65 volts, and one 127v to the am4 four heads.
I can't measure any impedance between the sides on the dcn601.
Does my troubleshooting seem right? Could i confirm my theory in any other way?
And, where cold i find a suitably transformer if its kaputt? 280 v dc in, 65/127 out?
Hi guys,
Sorry to revive this thread again. It's been very informative, thanks!
I'm working on a S65 that I recently picked up. It's in OK shape, a bit dusty and old looking, but it should work. After reading this thread, I decided to replace the rectifier and the most critical electrolytic caps. My question, since I'm not too experienced, is if you guys want to help me verify witch caps those are?
Next too that, when I opened it up to take a look, I inmidiatelly found a blown cap in between the fuse and the chassis ground. I can't seem to find it on the schematic though. I've included a picture of the part. Can anybody help me identify this? It says 0022 uF but the rest of the description is burned.
Thanks in advance!
Sietse
Sorry to revive this thread again. It's been very informative, thanks!
I'm working on a S65 that I recently picked up. It's in OK shape, a bit dusty and old looking, but it should work. After reading this thread, I decided to replace the rectifier and the most critical electrolytic caps. My question, since I'm not too experienced, is if you guys want to help me verify witch caps those are?
Next too that, when I opened it up to take a look, I inmidiatelly found a blown cap in between the fuse and the chassis ground. I can't seem to find it on the schematic though. I've included a picture of the part. Can anybody help me identify this? It says 0022 uF but the rest of the description is burned.
An externally hosted image should be here but it was not working when we last tested it.
Thanks in advance!
Sietse
All electrolytics in something of this age are going to be suspect. The three caps to the left of the bridge would be the favourites, C27 and C28a and C28b. They sound like a shared cap, two caps in one can having three leads. You would have to replace those with two individual ones.
The exploded cap I have no idea on. If it was by the mains fuse then its possible it could be a filter cap across the incoming mains (0.0022uf or 0.02uf ?). If so, then it will all work without it.
The exploded cap I have no idea on. If it was by the mains fuse then its possible it could be a filter cap across the incoming mains (0.0022uf or 0.02uf ?). If so, then it will all work without it.
Thanks for the reply Mooly! Yes, C27 and 28a/b was on my list. It looks like a shared one, yes, so I'll try and find 2x 32 uF and see how that goes. Just to be sure: electrolytics are marked with polarity on the schematic right? The other caps are other types I guess?
About the blown cap: yes it was by the mains fuse, so I guess it's a filter cap, put there by the previous owned maybe. Would it have a significant impact on the sound if I leave it out?
Thanks again for the help, much appreciated!
Cheers,
Sietse
You'll perhaps find that 33 or 47uf are the nearest common values used today. Yes, all the electrolytics are marked with a + sign for polarity. The other small value caps if replaced today would typically be 'film' types. I don't know what could have been used historically, there are paper in oil types, metallized paper, ceramic... many types. Unless you want historical accuracy then use modern replacements.
The filter cap would have no impact on the sound in practice. Filter caps today MUST be of the correct type which is Class X for connecting across the incoming live and neutral. Years ago metallized polyester caps were used and these failed with alarming regularity (and a big bang) even when they seemed suitably rated voltage wise. Filter caps are also used to stop noise getting out of equipment as well as getting in, although that's more of a modern problem with switching power supplies and so on.
The filter cap would have no impact on the sound in practice. Filter caps today MUST be of the correct type which is Class X for connecting across the incoming live and neutral. Years ago metallized polyester caps were used and these failed with alarming regularity (and a big bang) even when they seemed suitably rated voltage wise. Filter caps are also used to stop noise getting out of equipment as well as getting in, although that's more of a modern problem with switching power supplies and so on.
Yeah, I'm just going to replace te electrolytic caps. Got a little trouble finding the right values though, especially the high voltage. I understand that going a bit up with the cap value is no problem, and 33/47 uF are easy to find. none of them go above 450v though, and this one is rated 550/450. Although the schematic says there should be 300v and 255v running through them, I guess there's a reason the original design has a 550/450 rating? Or will two caps of 450v do as well?
Worst case condition for voltage across those caps is during valve warm up when no current is being drawn from the power supply.
Measure the voltage immediately after switch on across C26b, and base replacements on the measured result. Anything below around 420 volts DC will be OK to replace all three caps with 450vdc ones. I can't see the voltages being anywhere near that tbh.
There is a 240 vac marking on the secondary winding feeding the bridge rectifier which if correct would give a DC voltage across the caps of around 340 volts.
Measure the voltage immediately after switch on across C26b, and base replacements on the measured result. Anything below around 420 volts DC will be OK to replace all three caps with 450vdc ones. I can't see the voltages being anywhere near that tbh.
There is a 240 vac marking on the secondary winding feeding the bridge rectifier which if correct would give a DC voltage across the caps of around 340 volts.
Important things to remember with dividers.
1/ Resistors have voltage ratings which apply even if the calculated power is very low. For example you can not use a normal 10 Meg 0.25 watt part across 1000 volts DC even though the power dissipation works out to just 0.1 watts.
2/ Your meter has resistance that appears in parallel with any voltage you measure. If its a digital meter then the effect of that will be negligible. Some old analogue meters were a very different matter though. A typical digital meter is around 10Meg ohms per volt sensitivity, an AVO8 was 20K per volt (huge difference) and some really cheapo meters could be 1000 ohms per volt.
Voltmeter Sensitivity
1/ Resistors have voltage ratings which apply even if the calculated power is very low. For example you can not use a normal 10 Meg 0.25 watt part across 1000 volts DC even though the power dissipation works out to just 0.1 watts.
2/ Your meter has resistance that appears in parallel with any voltage you measure. If its a digital meter then the effect of that will be negligible. Some old analogue meters were a very different matter though. A typical digital meter is around 10Meg ohms per volt sensitivity, an AVO8 was 20K per volt (huge difference) and some really cheapo meters could be 1000 ohms per volt.
Voltmeter Sensitivity
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