I'm working on the reverb of this amp. The actual amp differs from the schematic in that it uses a 12ax7 for the first part of the reverb, instead of a 6an8.
The amp sounds really good, and I got the reverb going for about 30 minutes, before the(I think) 6AV6 made some weird crackly, and gave it up.
I ordered a "NOS" from ebay, put the new 6av6 in, and still no verb. This of course does not rule out the fact that the 6AV6 position is the issue.
So, I pulled the amp again and started poking around. It has had some general maintainence in the past, and here's my question :
On the schematic, on the triode side of the 6an8, there is a cap coming off the cathode divider, a 1U 150V(the 12ax7 has the same circuit). This was replaced with an electrolytic, whose + end points toward the cathode divider.
Is this backwards?
Univox 305r
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Smokebreak
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Univox 305r
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martin manning
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Re: Univox 305r
It's correct, positive end toward the cathode.
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Smokebreak
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Re: Univox 305r
Ok thanks Martin
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Stevem
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Re: Univox 305r
First off you need do to a resistance check on each of the pans RCA jacks and confirm that both are not open.
Sometimes the coil is open, other times a wire comes off at the RCA if your lucky, so I look close at the jacks.
Next every dam gray cased .01 cap in that amp needs to changed !
I have worked on tons of these and Lafayette's which are the same amps and when just one of these great sounding oil filled .01s go bad in short order so do many more!
Also note that the tube sockets used in these amps really really suck after 40 plus years!
Sometimes the coil is open, other times a wire comes off at the RCA if your lucky, so I look close at the jacks.
Next every dam gray cased .01 cap in that amp needs to changed !
I have worked on tons of these and Lafayette's which are the same amps and when just one of these great sounding oil filled .01s go bad in short order so do many more!
Also note that the tube sockets used in these amps really really suck after 40 plus years!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Smokebreak
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Re: Univox 305r
After addressing what seemed like a new problem every couple of days, I was left with intermittent tremolo. Narrowed it down to a bad socket! Thanks!Stevem wrote:
Also note that the tube sockets used in these amps really really suck after 40 plus years!
Oh, 4 6AV6s later, the one that came from Tube Depot was the one that worked
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Stevem
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Re: Univox 305r
Is that socket intermitant also? You may want to make sure that rocking that tube around in that socket makes for no crackling noises and that tube shows no sign of red plating in the dark!
And speaking of red plating that 10uf at 50 volt filter after the bias diode should be upped to a 50uf cap as 10uf is so damed small!
And speaking of red plating that 10uf at 50 volt filter after the bias diode should be upped to a 50uf cap as 10uf is so damed small!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Smokebreak
- Posts: 1391
- Joined: Tue Dec 18, 2012 5:53 pm
- Location: Texas
Re: Univox 305r
That socket(and the others) was fine. I rocked em all. I gave the amp back yesterday, and all the lytics had been replaced previously(as well as all the couplers you mentioned), but I'll add upping the bias cap to my upgrade list.
I will say this amp sounded really, really good. The owner had put a Blue Dog in it, and it reminded me of my 1624T, but warmer, and nastier when cranked. Pretty similar circuit.
Also, there were EH 6973s in, and while I have no real 6973s to compare to, I won't shy away from these like I have in the past, just because they're not "real" 6973s.
Reverb is kinda cheap sounding, but good in that swampy way. Trem sounded great.
I will say this amp sounded really, really good. The owner had put a Blue Dog in it, and it reminded me of my 1624T, but warmer, and nastier when cranked. Pretty similar circuit.
Also, there were EH 6973s in, and while I have no real 6973s to compare to, I won't shy away from these like I have in the past, just because they're not "real" 6973s.
Reverb is kinda cheap sounding, but good in that swampy way. Trem sounded great.
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Stevem
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- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Univox 305r
Cool!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Univox 305r
Cool amps I have one somewhere