VTL compact 100 issues
Jhayman
Posts: 1,548
VTL compact 100 troubles
My left amp one of my tubes I noticed was a little dimmer when powered on compared to the other 3 tubes.
It also has a black spot on the glass so I took out one of the other tubes and swapped them then powered the amp back on and the better tube started glowing bright red in a couple of seconds so I immediately powered off the amp and switched the 2 tubes back to their previous slots and everything is good, except for the same tubes being dim and having a black spot on it.
I hope I explained it right, but I'm guessing I need to get my amp biased correctly and possibly need a new tube?
I know its better to replace all the power tube together correct?
Also when I first power on the amps the left one sometimes crackles for a little bit first before settling down?
Thanks
My left amp one of my tubes I noticed was a little dimmer when powered on compared to the other 3 tubes.
It also has a black spot on the glass so I took out one of the other tubes and swapped them then powered the amp back on and the better tube started glowing bright red in a couple of seconds so I immediately powered off the amp and switched the 2 tubes back to their previous slots and everything is good, except for the same tubes being dim and having a black spot on it.
I hope I explained it right, but I'm guessing I need to get my amp biased correctly and possibly need a new tube?
I know its better to replace all the power tube together correct?
Also when I first power on the amps the left one sometimes crackles for a little bit first before settling down?
Thanks
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables
Comments
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I'd say you have tube going south, so yeah time for a new set. Are you not able to bias the amps yourself as you should check the bias every so often, like once a month.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks Jesse..
No I do not know how to check the bias..
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
Ok Jamie, you're going to have to learn. You will need to buy a VOM to start. Do your amps have bias points on the top? If so, is there a point for each power tube or one point for all?Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
WARNING!!!! There is very high voltage (deadly!!) in the tube amp (even when not on and unplugged) so be very very careful.
The bias points are many times found on the circuit board. It will vary from being a single point or one for each channel. I believe one bias point for each channel is most common however (that's how my tube amp is). There should be adjustment pots (potentiometers) next to the bias points and you simply turn them while placing the VOM leads on the bias points until you match the correct values. This is after you install the new tubes and let the amp warm up fully.
Edit: I just read that the bias points and pots are "on the top" as Jesse referred to.
Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
"I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion."![:\](https://forum.polkaudio.com/resources/emoji/confused.png ":\")
My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....
"Green leaves reveal the heart spoken Khatru"- Jon Anderson
"Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee -
Ok guys Thanks..
First I'll get a VOM this weekend and check my amps for the bias points which I'm not sure if they are on top or under..
I'll be very careful where I place my hands while looking around..ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
Taken from a recent Audioholics reply regarding "Club Polk" and Polk speakers:
"I'm yet to hear a Polk speaker that merits more than a sentence and 60 seconds discussion."
My response is: If you need 60 seconds to respond in one sentence, you probably should't be evaluating Polk speakers.....
"Green leaves reveal the heart spoken Khatru"- Jon Anderson
"Have A Little Faith! And Everything You'll Face, Will Jump From Out Right On Into Place! Yeah! Take A Little Time! And Everything You'll Find, Will Move From Gloom Right On Into Shine!"- Arthur Lee -
Thanks headrott..
Also took a couple of pics if I'm understanding correctly I believe I know how to do it..
Just a question or two to ask..
In the first pic you can see the blue trim pot I believe that is the master, as the other trim pots are up an inch to the left and beside each other?
Same on the other side the two trim pots are beside eachother only the one you can see in the pic is below the others so I guess it's the master controller?
And the measurement points for each tube is the black holes with the little metal in the hole put the positive VOM probe in their and negative probe on negative speaker terminal and set to ohms should be about 10 according to VTL.
Then power on with speakers connected switch to millivolts and adjust pots to 250-300 for each tube, then after I can use the master to adjust all for weekly or monthly inspection..
Does that sound about right?
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
Well we have an update, I've read the required reading for VTL amp biasing.
The right amp tests fine at 10ohms to 10.2 on some which is fine.
The left was fine until I got to the two forward tubes as seen in pic 2.
The two back tubes test within spec which is 250-300mv
The two forward tubes read ZERO on the meter..????but are glowing like normal except for the tube I first told you about..in first post.
What should be my next course of action?
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
It was actually easier than I thought to Bias the amps..
I just was not sure where the bias points were, now in PIC 2 you can see them plain as day in front of each tube but I thought they were screw holes, lol
My eyes are going fast definitely need glasses now..
but like I said the 2 forward tubes measure Zero where as everything else measures within spec after I adjusted them..
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
A tube can be bad and still glow. Another possible issue, the bias resistors could be bad.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks Jesse..
I did not know a tube could still glow and be bad, I thought they were like light bulbs the filament breaks and that's it..
Considering that when I swapped the tube with the black spot with the one to the above/right it started to glow cherry red what would be your conclusion then?
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
Either the bias was really off and/or the bias resistor is bad,Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks Jesse.
I did turn the pot all the way to left and right with no change on the two front tubes..
So I guess there are two bad bias resistors..
So off to the tech guy to fix I guess..
ATC SCM40's,VTL TL 2.5 Preamp,PSB Stratus Goldi's,McCormack DNA 500,McCormack MAP-1 Preamp,Pro-Ject Xtension 10 TT,Ortofon Cadenza Red/Nordost RedDawn LS Speaker cables, Bryston BDP-2, Bryston BDA-2,PS Audio AC-3 power cables -
If you can solder that would be an easy fix. The values will be printed on the resistor(s).
That said, I'll repeat what Greg wrote,WARNING!!!! There is very high voltage (deadly!!) in the tube amp (even when not on and unplugged) so be very very careful.
Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
And,,,, careful with the master bias
JC approves....he told me so. (F-1 nut)
