Well, a TSL50 beats no TSL at all...

[Dave W]

Good to hear you have sound from an actual amp! I am not an expert, but I do not understand why the impedence switch would be set to 8 ohms. If your cab is 16 ohms then I believe your amp impedence switch should be set to 16 ohms also even if you just have 2 power tubes running. Unless I am ignorant to this method which is always possible, dropping to 2 power tubes does not mean you cut the impedence in half. You will be affecting the electronics in a way that only an amp expert can explain, but even if if 2 tubes affects the resistance and draw and whatever other factors I still think it should be run with the matching inpedence for the amp and cab till you hear a response otherwise from an expert in these matters. I have read about people doing this to attempt to decrease volume a little and do not remember about decreasing the ohms matching etc. Now I could be totally wrong on this and if so I am sorry for that. Its possible there is an old thread on this forum, I know about a month ago there was a long thread about power tube substitutions for the VM and seval posts mention the issue of using different tubes and if you could go from 4 to 2 on the VM 2246. I believe the post title was in regard to putting EL34's in the VM and the discussion went on from there. I have mismatched impedence before by accident an no problems but the risk is always there to kill the amp. You might want to wait till you here from others before using alot. Also, I do not know the exact condition of the sockets and board, do you think itspossible that the sockets are fried but possibly the board may be alright? Maybe you could replace the sockets and give it a try? Use your old tubes if you do this, at least the power tubes. You might fry the amp or it may work depending on the circuit board. You can buy sockets online. If you can not get them from a tube place then try Weber Speakers or just google Tube Sockets and something should show up. Its a crap shoot though as far as what to do. Glad you have a working amp though!

[lowenzz]

I haven't had anything to say about my busted TSL100 until I could get it back and see what's what. Once I did, I could see what the guy was talking about, but it only looked like the sockets for V6 and, possibly, V7 were damaged. The tubes looked beat, too, but I don't have a tester to verify. Thanks to y'all's donations of $125.00, I was able to get a pair of Winged "C"/SED EL34's and four JJ ECC83S's for $140.00.

I replaced V1-V4 and put the EL34's in the two outer sockets. Biased it at around 43mv per side, and ... IT WORKS! Woo-Hoo! I guess, until I can afford &/or find a PCB, I have a TSL50. And, as the title says, a TSL50 is a lot better than no TSL. At least I have something to play besides a crappy ME-50 into my old computer. It sounds like a guitar!

I appreciate everybody who helped me out. I said before, you guys are the best!

Just to verify that I'm doing this two tube thing right: 43mv per side. Speaker cable from the 16ohm output of the head to the 16ohm input of the 1960AV. Impedance switch set at 8ohm (does this even matter?)

As far as I know your impedence switch now indicates 1/2 the rating. In the 16ohm position it is now actually 8ohms, in the 8 ohm position it would be 4 ohms. FWIW Im not absolutely sure on this, hopefully someone else will chime in on it. Good Luck.

[DeanM]

im not really sure what the whole story is behind whatever youv done with yer tsl, but if its putting out 100watt set at 16ohm when it goes to the cab it will match and put out 1oowatt. but if its putting out 100watt at 8ohm and the goes to the cab and meets 16ohm, that is twice the expected impedence and so the output will be halved to 50watt. maybe thats why the impedence isnt matched correct.

im just goin by ohm's law cos as i said i dont know what else ya'v done tube-wise or how it will effect the amp. so without knowin exactly whats been altered i can only go on what i see here!! hope dis helps!!

[surfnorthwest]

Hey glad we could help out a little. Nice to see you back up again.

[MKB]

Hey Altanon, it's great to hear you got your amp up and running!! I hope you can get the rest of it fixed eventually; it would probably be good to get a second opinion on needing a new circuit board. I'd doubt you would need the whole board replaced if the amp works OK with two power tubes, that tells you most of the board is OK. The sockets should be replaceable without changing out the board.

According to the TSL schematic I just looked at, the TSL doesn't have a choke, which means it might have the same condition as the VM in that it may not be safe to use just two power tubes, but I'm not at all certain about this. Hopefully Steve D can say whether it is safe to use it like this or not.

Transformers do not actually have a specific impedance, they in fact "transform" one impedance to match another impedance. When an output transformer is specified to match a quartet of EL34's to a specific speaker load, it actually is designed to match the plate load of the tubes (which is usually several thousand ohms) to the low ohms speaker load.

When you change the load on the primary (actually doubling the load by removing a pair of tubes), the transformer is then wanting to see a different impedance on the secondary in order for the loads to match. As long as the impedances match, in most cases the transformer doesn't care at all what the exact primary or secondary impedances are, it is operating correctly and is in no danger of damage.

In the case of a 100W Marshall, the primary impedance is generally around 1800 ohms to a secondary of 16 ohms. This is to match the power tube impedance of around 1800 ohms to the speaker load. If you pull a pair of tubes, the power tube impedance at the primary goes up to 3600 ohms, so the fixed transformer tap ratio causes the output impedance of the 16 ohm secondary to functionally increase to 32 ohms (to retain the impedance match). The 8 ohm transformer tap with 4 tubes is now at 16 ohms to match the two power tubes; this is why you have to use the next lower impedance tap to get the closest match.

So with 4 tubes, your secondary taps are at 16, 8 and 4 ohms. With two tubes, the taps are 32, 16 and 8 ohms. If anyone is interested, I can dig the books out and describe it with a little math. It can be a little confusing, hope this clears it up a bit...

[Dave W]

I just learned some new stuff here today from the posts. Sorry abou tmy uneducated response. My advice would have been a bad move. I am glad others chimed in. Enjoy the amp!

[DeanM]

I just learned some new stuff here today from the posts. Sorry abou tmy uneducated response. My advice would have been a bad move. I am glad others chimed in. Enjoy the amp!

Me too!! MKB's post was interesting!!