Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on October 21, 2011, 08:40:04 am

Title: Replacing Filter caps
Post by: pbman1953 on October 21, 2011, 08:40:04 am

Amp-

Traynor YBA-3A Super Custom-

Even though I replaced the larger filter caps already, with "TH" Caps. they went bad. I need a suggestion on what to use

The original Can cap was 200mf @ 350 volt. I replaced with 2- 220's @ 350V in series.

Any suggestions?

here's the map-
http://www.freeinfosociety.com/electronics/schematics/audio/traynor_customspecial_yba3a.pdf (http://www.freeinfosociety.com/electronics/schematics/audio/traynor_customspecial_yba3a.pdf)

Title: Re: Replacing Filter caps
Post by: phsyconoodler on October 21, 2011, 01:01:24 pm

What do you mean they 'went bad' ?

Title: Re: Replacing Filter caps
Post by: pbman1953 on October 21, 2011, 01:22:32 pm

The amp has a severe hum and I called Traynor and they heard the hum over the phone. They told me with the filter cpas cut out of the circuit the noise would get worse. It didn't it stayed the same. After that they felt it was a bad filter cap. Possibly one of the cpas went bad internally.

Title: Re: Replacing Filter caps
Post by: rafe on October 21, 2011, 03:28:50 pm

You did not mention C-32&C-33 (40/450v) did you also replace them?There is atually another C-32(8-150v)that may be electolytic C-31 looks like the death cap is it still there? C-25(8-150v) C-26(100-150)...I may be way off base here, but I'd check all the caps on the schematic that have voltage ratings to make sure they are not electrolytic and bad.....

Title: Re: Replacing Filter caps
Post by: pbman1953 on October 21, 2011, 03:33:47 pm

I've replaced every cap in the amp

Electro to new electro's and any non-electro to mylar or polyester

Title: Re: Replacing Filter caps
Post by: phsyconoodler on October 21, 2011, 05:49:03 pm

The chances of those caps just 'going bad' are so rare it leads me to believe something else is amiss.
  what about the heaters?Do you have the center tap well grounded or are using 100 ohm resistors?

Title: Re: Replacing Filter caps
Post by: pbman1953 on October 21, 2011, 06:17:59 pm

Each tube is well grounded. I do have one lifted ground in the amp that I had to jump to another spot

Title: Re: Replacing Filter caps
Post by: phsyconoodler on October 21, 2011, 06:57:45 pm

I'm talking about the heaters."Each tube is well grounded"

That is not an issue.A picture is worth a thousand words.
 Your noise may not be a 60 cycle hum but a heater hum.

Title: Re: Replacing Filter caps
Post by: pbman1953 on October 21, 2011, 08:31:12 pm

So what should I send a  picture of

Title: Re: Replacing Filter caps
Post by: pbman1953 on October 22, 2011, 09:18:50 am

If your looking at the schematic and wondering about the 100 ohm resistor (r39), it reads 100 ohm. R9, also a 100 at one of center preamp tube. also measures 100 ohm

Title: FIXED
Post by: pbman1953 on October 22, 2011, 01:19:48 pm

I went to my local parts store and picked up a pair of NTE- 220 uf @ 450v and and it's quiester than ever

Thanks for all the input!!