Orange Thunderverb 200 B Channel Has Insanely Low Output

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mkat13
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Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by mkat13 » Sat May 28, 2016 3:51 am

Hello. I am a longtime Orange player. I own the TH100 and AD30 HTC heads with Orange 4x12 cabs and a Rockerverb 50 2x12 combo. I am pretty familiar with the brand and fairly savvy with tube amps in general or so I thought. I can re-tube and bias my own gear etc. I just picked up a second hand TV200 and noticed that the output is borderline nonexistent on the B Channel at low volume and gain and there is literally zero difference until its almost full bore when the attenuator is rolled to 3 O'Clock or so. This is not at all the case with the A Channel. Is this normal for the model?

Les Paul Lover
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Location: Derby, England

Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by Les Paul Lover » Sat May 28, 2016 9:55 pm

Not sure I totally understand your issue.

So with the volume & gain set low you can't t hear anything ?

That's about the same with my RV50 and current R30.

But as I gradually turn up the gain, with the volume still low, ( just past the 1st notch) both volume and gain increase, and I believe your TV200 should be the same. (nevermind the attenuator here).

If that aspect of the amp works fine, that's a start, otherwise I would look into the preamp / power valves. (since you say that you believe channel A is behaving as you should expect, I think the preamp valves are the likely culprit.)

If the problem only happens with the attenuator engaged, 8k not sure what to suggest. The attenuator is essentially a ppi (post phase inverter) master volume, so if it does cause problems with only one channel, that would be very curious indeed.
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


Guitars: Gibson Les Paul Standard Faded, Vigier Expert Retro 54, Gibson SG 70s Tribute, Aria Pro II RS X80, G&L ASAT Special Tribute

mkat13
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Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by mkat13 » Thu Jun 02, 2016 3:17 am

Hey Man, thanks for the reply.

After fiddling with the TV 200 a bit more it just seems like there is no significant output from channel B in comparison to channel A. If I have Channel A volume at 7 or 8 O'clock and Gain at Noon it is what I would expect, not incredibly loud but above bedroom volume by several clicks, if I increase the volume it gets very loud indeed. If Channel B is is set identically it is not even close. I cannot get any significant volume increase in Channel B without cranking both volume and gain to full bore. In this instance as described for both channels, the attenuator is wide open and the volume is not inhibited. So, it seems like the B side is a bit wacked. Do you suppose a retube/bias will sort this or is it more than that?

Phlowen
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Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by Phlowen » Thu Jun 02, 2016 3:36 pm

It certainly could be a tube issue with the B channel, and it would most likely be the preamp tubes (I'm assuming both channels use the same power tubes...meaning the issue isn't anything to do with biasing).

This is a bit of an odd scenario since channel A and B both use the same tube for their first gain stage...I suppose it'd be theoretically possible for 1/2 of the shared preamp tube to be failing as well...

I'd start with swapping out the 1st preamp tube (bottom right tube in the image below) with either the bottom center or bottom left tubes and see if the problem travels. If it does move (now channel A is quiet and B is loud) you know you need to replace that first tube, which was previously in the bottom right position.

If it DOESN'T move...replace those first two tubes to their original locations and try swapping out channel A and B's 2nd&3rd gain stage preamp tubes (the bottom left and bottom center tubes in the image below) and see if the problem moves with the tubes. Again, If it DOES move you know you've pinpointed the issue. If it doesn't, you've completely ruled out the channel specific preamp tubes.

(Apologies if this explanation is overly pedantic. I try to not assume anything about your level of knowledge and explain as much as possible...please don't take it as an insult!)

Here is the tube layout for the TV200:
Image
RV 50 MKI | TH30 | RV 50 MKIII
G&L Tele (ASAT Classic) | Musicman Bongo 5
Anesthesia - Post-Rock/Ambient band - anesthesiaproject.com

mkat13
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Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by mkat13 » Fri Jun 03, 2016 1:37 am

Phlowen, thanks for the additional insights and the diagram for reference. Im going to retube the whole amp and give it a fresh bias and see what happens. Thats about the extent of my ability to trouble shoot/repair. I'll report back. As far as the detailed description of troubleshooting scenarios goes, I appreciate it! If this turns out to be totally non tube related, what are other likely culprits? Bad capacitors or resistors? Im pretty much an amp repair novice so please bear with me as I try to learn this stuff. By the way, Anasthesia is really good, super cinematic. Later for now.

Phlowen
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Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by Phlowen » Fri Jun 03, 2016 2:00 pm

Hey, thanks! I really appreciate that!

If you're already going to take it to a tech to get it biased (which you definitely should as biasing is tricky and potentially lethal if you don't know what you're doing) they should be able to pinpoint the issue if it's not tube related. I would be surprised if it was something else, but do let us know when you find out!
RV 50 MKI | TH30 | RV 50 MKIII
G&L Tele (ASAT Classic) | Musicman Bongo 5
Anesthesia - Post-Rock/Ambient band - anesthesiaproject.com

mkat13
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Joined: Sat May 28, 2016 3:23 am

Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by mkat13 » Fri Jun 03, 2016 10:02 pm

I can retube and bias it myself, I just dont know how to do anything else at this point. Will report back.

Phlowen
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Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by Phlowen » Fri Jun 03, 2016 10:13 pm

Drain those caps!
RV 50 MKI | TH30 | RV 50 MKIII
G&L Tele (ASAT Classic) | Musicman Bongo 5
Anesthesia - Post-Rock/Ambient band - anesthesiaproject.com

Les Paul Lover
Duke of Orange
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Location: Derby, England

Re: Orange Thunderverb 200 B Channel Has Insanely Low Output

Post by Les Paul Lover » Sun Jun 05, 2016 10:14 pm

By the way, I reckon your power valves are fine.

If they were damaged, the same problem would be there on both channel. If it is a preamp valve problem, just do as Phlowen recommended.

Obviously free to you to get new power valves, but this will not help you with the current issue.

If it isn't a valve, it's tech time really. It could be a lot of things, a unwanted ground draining some of thw signal, a failed potentiometers, damaged resistors / capacitors....
Ant

Orange Gear: RV50 MKI, R30, AD15, PPC212
And.... Genz Benz Black Pearl 30
Past Orange: AD30TC Combo, TT, AD5


Guitars: Gibson Les Paul Standard Faded, Vigier Expert Retro 54, Gibson SG 70s Tribute, Aria Pro II RS X80, G&L ASAT Special Tribute

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