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**Gtr_tech** · 02-27-2010, 01:56 PM

Bad caps can cause strange things to happen. You'll be better off with the 500v replacements as the 450v will likely be overvoltaged now due to higher line voltages. I just picked up a 71 Custom Reverb head and I have 468v on the first 2 cap sections rated for 450v. So those will be replaced with 500v parts, but I'm going the opposite way as you. This has a 40/40 cap for the plate/screen supply. I'm going with a 100/100 to stiffen it up some. Since there's no choke I want the extra reserve on hand.

I also disabled the tremolo. Why? Because it passes bias voltage thru a pot on its way to the output tube grids. Do pots go intermittant? Absolutely. This is bad mojo.

**SilverTone439** · 03-09-2010, 12:28 PM

Thanks for the reply GTR Tech. I have some questions.As I said I have the YGM-3 Guitar-Mate with 3 input on front.It has reverb and tremolo also.I compared all the different schematics including the re-issue one.I have 4 old style carbon resistors that I want to replace with flameproof style but they all seem to be different then whats on any schematic I find. R41 is 12 ohm brn. red blk. sil. R40 is 56K grn. blu. orn. sil. and last two are 220 ohms red.red.brn.sil. and 68 ohms blu. gry. blk. sil. Also caps C28 and C29 are a matching pair of 8uF 250v but schematic shows C29 should be 68uF 64V.Also should I leave the old Holland mustard caps or change them to SOKO's from MetroAmp? Also I noticed someone already put a three prong plug in but just but green ground wire is not hooked up.This also has the dreaded ground switch still hooked up and I am not sure what cap(death cap) everyone keeps talking about.Is it the small ceramic looking one from ground switch to ground? I am going to hook up the cord green ground wire to ground but not sure how to unhook/bypass the ground switch.Thanks for any advice or diagrams.I have uploaded 10 pics also.

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**SilverTone439** · 03-09-2010, 12:47 PM

Well I was checking through schematics and it appears this YGM-1 is what matches up to mine.

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**ThermionicScott** · 03-09-2010, 05:38 PM

Wouldn't hurt to replace the cathode bypass caps while you're in there. 22uF/50V would be a good replacement for those 25-25s.

- Scott

**SilverTone439** · 03-12-2010, 01:30 AM

My amp is missing the 250 ohm 10 watt resistor coming off the #3 of the top right 6BQ5 tube. This would be a rather large resistor and its not there however the amp worked fine for several years? Any input on this? Also mine has the pair of blue 8uF 250 caps side by side and this above YGM-1 schematic is not showing it. However mine does have the 3 transformers and all the carbon comp.resistors match up. My amp has the 3 inputs in front but YGM-1 circuit matches and not the YGM-3? Thanks

**rf7** · 03-12-2010, 01:55 AM

Originally posted by SilverTone439 View Post

I am not sure what cap(death cap) everyone keeps talking about.Is it the small ceramic looking one from ground switch to ground? I am going to hook up the cord green ground wire to ground but not sure how to unhook/bypass the ground switch.Thanks for any advice or diagrams.I have uploaded 10 pics also.

Yes, that's the death cap. You can just remove it and you're good to go. Replace those light blue electrolytic caps, they usually go bad with age.

**Bruce / Mission Amps** · 03-13-2010, 04:26 AM

Originally posted by SilverTone439 View Post

My amp is missing the 250 ohm 10 watt resistor coming off the #3 of the top right 6BQ5 tube. This would be a rather large resistor and its not there however the amp worked fine for several years? Any input on this? Also mine has the pair of blue 8uF 250 caps side by side and this above YGM-1 schematic is not showing it. However mine does have the 3 transformers and all the carbon comp.resistors match up. My amp has the 3 inputs in front but YGM-1 circuit matches and not the YGM-3? Thanks

That would be a fixed bias amp and the 8uF caps are your bias supply filter caps.
Replace them with 10uF@250v-350v caps.
Leave all the mustard caps alone unless they are bad...

**SilverTone439** · 03-14-2010, 04:11 PM

I removed the death cap, hooked up the green ground wire to chassis transformer bolt with star lock washer,replaced both 40/40uF 450v main filter caps with two new 50/50uF 500V and clamps from Angela.com.One of the old can style caps tested bad on analog meter and rattled inside when shook meter would not bleed off when probes reversed.Replaced all the mustard caps with new Soko's from Metroamp.Replaced all the old blue caps with new Sprauge Atom's.solderer speaker wire onto speaker terminals,ran new speaker heavy ga. wire.Replaced all tubes with new matched JJ's 2 EL84/6BQ5's and 4 12AX7's. I did not touch the old carbon comp. resistors but if I do I will use metal films 1 watt only.Fired it up and the Oxford speaker really sounded great.Volume on 3 and sound's unbelievable.I posted some before and after pics.I appreciate this forum and all the expert advice.It really came in handy when I was doing this re-cap.I thought hey if I don't like the Soko caps I will just put old Holland mustard caps back in.But I love it and see no reason too.

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