Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on August 23, 2011, 06:13:16 pm
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HI
I’ve had the amp now for at least 7 years and it seems that it’s lost some zing to it. When I first bought it was scary like an SVT. Even though I’ve replaced the silver can caps and went discrete. It sounds great but doesn’t have that zing like I think it should have. The amp first came with EI tubes and now I use Svetlana winged c’s. Recently I switched back to the EI’s just to see if there was a sound difference and the winged c’s still won.
How do you know if a transformer is losing power? Does that happen?
Any help would be appreciated
Thanks
Rich
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Bias,tube life,your ears. Hard to say.Tubes are the number one culprit and of course what they are biased at.
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This is amp is real easy to Bias. On the schematic you'd see a line that shows 100ma. All you do is place a meter between this red wire and the connecting point of the wire and set to 100ma. It's cut and dry and the tubes are set like that
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Preamp tubes? Your speakers getting worn out? Your guitar cables?
Lots of variables and who knows how good the tubes are that you have in there?There is no guarantee that one set of tubes will be identical to another set even at the same bias setting.
Get your tubes tested and get another set to try.Yes,it's expensive but what you are asking us to figure out sometimes can't be quantified.
Your perceptions change and maybe you got a new pedal or are playing in a different room.
There are too many things to pinpoint any one thing with the very limited information you are giving.
And no,it's almost unheard of for your OT to be bad.It's the last on the list by far.
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Rich,
I cannot think of a way a transformer could "Loose Power"
At least not in the way I think you are intending.
I'd have to give a big +1 to Pscho's ideas.
What amp are we talking about anyways?
Did this problem occur after you replaced the "silver can caps" ?
And by going discrete, do you mean you've replaced a rectifier tube with diodes?
Also, are you playing a bass into this amp? (you mention a SVT) and what speakers are you plugging into (do they have a horn with a cross over?)
Ray
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What amp are we talking about anyways? Traynor YBA-3A Super, the 250 watts amp
Did this problem occur after you replaced the "silver can caps" ? Don't think so, I think the amp had better sustain after the update
And by going discrete, do you mean you've replaced a rectifier tube with diodes? I've gone through this amp. Updated small caps and changed out the carbon (brown) resisitors. No diode changes
Here's the schematic- http://www.freeinfosociety.com/electronics/schematics/audio/traynor_customspecial_yba3a.pdf (http://www.freeinfosociety.com/electronics/schematics/audio/traynor_customspecial_yba3a.pdf)
Yes I'm playing bass running thorugh these cabs-
Ampeg Pro Series- 4 x 10 - 8 ohm
JBL Caberay series with a E140- 8 ohm
Sunn 200s cab w/ 2 x 15- K140's- 4 ohm
If I want, I can use all of them in the 2 ohm mode of the amp. I take the JBL & Ampeg in parallel to get 4 ohm. The Ampeg has a tweeter but it's not used hardly
Thanks
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I called up to Traynor today and luckily spoke with Guy. He was on the original service team during the days of my amp. He also mentioned that it could be tubes. We went over the bias setting itself and he made further calculations that I could beef up the 100ma amount up to 150ma. He really likes the 6Kg6 tube and he said it could take a hotter setting
I may give that a try and see what happens. I'll look into a new set too
Thanks
PS- most of all he gave me the best tip for any tube amp owner. After installing and biasing a new set of tubes , run the amp , with no load for 96 hours. That 96 hours of burn in could first see if you have any problenm tubes plus it helps extend the tube life the burn in.
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After installing and biasing a new set of tubes , run the amp , with no load for 96 hours. That 96 hours of burn in could first see if you have any problenm tubes plus it helps extend the tube life the burn in.
with no LOAD or no SIGNAL??
Huge difference.
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no signal , just sitting there but on
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Just be sure, and I should have specified this when I posted earlier, that you do not have a shorting phone jack or other connector on the output of your amp when you do this. If the secondary of the OT is open, that is one thing. If it is shorting jack, like on a deluxe reverb that's quite another! It's probable that a separate head + speaker amp would NOT have a shorting jack on its output, but if it were me, I would not do this "for 96 hours" without a bare phone jack plugged into the speaker output, or, alternatively, a guitar cord connected to nothing. Sure can't hurt.
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What kind of capacitor you put in place the originals silver can ? A low quality brand can make difference in sustain , headroom.
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Just to clarify, that I never said not to have a speaker connected. I thought with any tube that it's a must noit to run without a speaker connected. What I meant was to simply set up at normal just just to run with no input signal
As fars as cap I get them from Antique Supply in AZ. I think they were F&T
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Pictures of the caps
The dark blue ones
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Any comments on these caps?
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No Comments on thses caps?
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I thought they were black. :grin:
I don't like the cable tie around that smaller cap and big power resistor.
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Thanks for the heads up, I can fix the tie wraps.
Are those caps ok, will another brand make a difference?
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Are those caps ok,
yes
will another brand make a difference?
no
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thanks