Thunderverb 200 Output Power and Reverb Valve

[mynamesidare]

Hi! Last night I bought a second hand Thunderverb, I've previously owned a Rockerverb 100 mkii and a Tiny Terror, and this is the tone for me! I love it!

Sorry if this has been answered a million times, I've done a forum search and a google search but am having trouble finding my answer, the manual doesn't even really answer the question. With the output power, you get the option of 200w or 2 different 100w settings, straight forward enough. My question is what is the different between the 1+3 and 2+4 settings? Some sort of valve config?

Also, the reverb on this amp is a bit knackered, as I bring the level of it up no reverb is present and the tone becomes mushy, distorted and weaker. My assumption is that the valve responsible is dead, but I wanted to ask to see if anyone knows otherwise before I throw a new valve in there!

Thanks!

[bassdrop]

Yes, the output tubes work in pairs, either the 1 +3 pair or the 2 + 4 pair. If you use the head in 100 watt mode often then you will want to switch back and forth between the tubes so that they wear out evenly. If you have a tube blow in the middle of a performance that switch can come in handy then too.

I would guess that you're having an issue with your reverb tube. You can take the first preamp tube from the channel you don't usually use and swap it into the reverb position to make sure that its the tube itself. Otherwise it might require a visit to the tech to get sussed out.

[mynamesidare]

That was pretty obvious really wasn't it? what a dumb question to ask! haha!

Thanks, will try that out tomorrow!

[Phlowen]

Not a dumb question at all! At the very least, it pays to have a hunch confirmed by a second opinion. One of the many reasons I love this forum!

[a.hun]

Main thing to watch out for is the different output impedances at the different power settings. Gets a bit confusing with that amp, but you DO want to correctly impedance match the amp output to the speaker load.

Yeah, if not sure about something then asking is never dumb.


Andy.

[mynamesidare]

Thanks for your help everyone

[mynamesidare]

So, I replaced the reverb valve last night with a new JJ ecc81 (or whatever the other name of it is, I can never remember the other code), and I still have the same issue. So that's my theory out of the window! Does anyone else have any other ideas? I guess the next step is to see if there is any loose cabling. I opened up the reverb unit a couple of days ago, looks in perfect condition so that wouldn't be the problem. If the unit was wired up backwards you wouldn't have this kind of distortion / almost phase issue would you?

The amp certainly isn't new and one of the power valves is practically dead, infact I realised all the tubes are the original orange branded valves, so in the near future I'm going to take it to an amp tech to get the power section changed out and re-biased, so I'll probably ask to have the verb looked at. Although, realistically I'm not too worried as I'm not a big spring reverb fan so it's not the end of the world, I just want everything to be working correctly!

[bassdrop]

I'm not sure why you would think that the tubes are dead if it is working in full power mode. It may be that one of the 6550's heaters does not light as brightly as the others? Depending on the year of your head's production you may have Winged C SED 6550C's which are the best 6550s produced since General Electric stopped production in 1989. The Winged C's have brown plastic bases; if they are metal bases they are most likely JJs and generally don't last super long but you can get several years of hard playing out of a set of Winged Cs. So keep that in mind before you take it in for servicing. A good tech will be able to test the 6550s to see if they are at the end of their life or still have some juice left in them. I would recommend taking it to the tech for your reverb issue at this point.

[mynamesidare]

I'm running at 100w with tubes 1 and 3, set to tubes 2 and 4 or 200w I get a pretty loud hum and a weaker sound, that to me suggest one of the power tubes have had it l on the way out

[bassdrop]

Could be one of your phase inverter tubes. The AD200 has a phase inverter for each pair of output tubes; I'm not totally sure if the TV200 is setup the same. I've had a PI tube go out and distortion and reduced volume is what happens. When an output tube goes you will usually blow at least one fuse. As the tube ages it will lose treble and output but won't be overly distorted; just kind of weak sounding. So it could go either way but if you have Winged Cs in there, let the tech test them and see if they're still any good.

[mynamesidare]

There is one phase inverter shared between both channels, I mean by deduction, surely if I can isolate the problem through switching the power output to 100w 2&4 (and obviously 200w / all valves doesn't narrow anything down) the chances are likely to be coming from there? I could be totally wrong and it be somewhere else, but that seems to make sense to me anyway! I'll get it booked in for a service next month, someone more knowledgeable than me will be able to figure it out!

[Phlowen]

If you're really curious if that's the issue, swap your 2 & 4 with your 1 & 3 power tubes and see if the problem moves with the tubes.

[jontheid]

This could well be a heater-cathode short in one of the power tubes.
As Phlowen says, if it moves with the tubes, it is the tubes.