hot time in the old cap tonight....

Posted by vinnie2 (A) on April 18, 2016 at 05:58:10

The attached schem is for my version of willie's 26/26/45 amp, at least I think it is. I drew it up back when I breadboarded the amp. It was working at that time and sounding good. I am now building the final version and I have run into a snag.
The cap on the cathode resitor of the 45 on the right channel blew up on me when I was bring up the B+ voltage after having checked the filament voltages and adjusting them. I looked everything over and could not see any errors so I thought just maybe it was a freak bad cap. Put in another and kept a close eye on it this time and sure enough it started getting hot and the end bulged a tad before I shut it down.I am guessing it was on it's way to blowing again.
So my first question is a general one. Does anyone see any thing in the schem that would make this a non-functional circuit? I might have made a mistake copying it down as I built the breadboard.
My second question, if the circuit appears alright, what would be likely to cause problems with the cathode cap? I checked the hum pot and the resistor and they seem ok. Iam puzzled once again.

Correction!!
Just noticed that I put in the operating points for the 45 and said they were for the 26. The 26 points are actually

plate volts 105vdc
plate current 6mA
grid volts -4.5
cathode resistor 820 ohms
bypass cap is 100uf/35vdc

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Topic - hot time in the old cap tonight.... - vinnie2 05:58:10 04/18/16 (21)

RE: hot time in the old cap tonight.... - maxhifi 09:13:05 04/18/16 (5)

RE: hot time in the old cap tonight.... - vinnie2 11:00:12 04/18/16 (4)

RE: hot time in the old cap tonight.... - Alpha Al 13:41:08 04/18/16 (3)

RE: hot time in the old cap tonight.... - vinnie2 18:07:38 04/18/16 (0)

RE: hot time in the old cap tonight.... - maxhifi 14:12:31 04/18/16 (1)

RE: hot time in the old cap tonight.... - vinnie2 18:09:46 04/18/16 (0)

RE: hot time in the old cap tonight.... - drlowmu 09:04:05 04/18/16 (1)

RE: hot time in the old cap tonight.... - vinnie2 11:06:02 04/18/16 (0)

RE: hot time in the old cap tonight.... - deafbykhorns 07:10:54 04/18/16 (0)

Sometimes it is hard to tell which end is up - Chip647 06:11:59 04/18/16 (11)

RE: Sometimes it is hard to tell which end is up - vinnie2 06:49:21 04/18/16 (10)

pics, etc - vinnie2 08:10:08 04/18/16 (6)

One of these things is not like the other - Chip647 12:17:37 04/18/16 (5)

RE: One of these things is not like the other - vinnie2 13:37:49 04/18/16 (4)

No, those suckers get really hot - Chip647 14:19:34 04/18/16 (3)

RE: No, those suckers get really hot - maxhifi 16:47:32 04/18/16 (2)

RE: No, those suckers get really hot - vinnie2 18:12:21 04/18/16 (1)

RE: No, those suckers get really hot - maxhifi 20:00:35 04/18/16 (0)

Can you post a picture? (nt) - Chip647 07:14:44 04/18/16 (0)

RE: Sometimes it is hard to tell which end is up - TRUFI 07:08:55 04/18/16 (0)

RE: Sometimes it is hard to tell which end is up - Triode_Kingdom 07:00:18 04/18/16 (0)

hot time in the old cap tonight....

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