Ampeg VL-1002/Please help..

[5150 TONE]

Hello. And welcome to my nightmare..I have an Ampeg VL-1002 my question is this amp has 7 preamp tubes in it 2 are not working (its the tubes not the sockets) I switced a few around to check, my problem is I do not know what each preamp tube is doing in this amp...and I looked on line for schematics and I can not make heads or tails from them..and after switching the tubes around and not making sure to put them back in the same place the amp is now making more hiss then before..So I ordered 7 new pre's 1 balanced for the phase inverter...now I just need the info on which tubes do what in this amp... Here is what I see from the back of the amp Am I right? Tranformer V6 V5 V4 V3 V2 V1 4 Kt-88's then V7. I will appriciate any and all help with this matter..Thank you all for looking..

[Enzo]

Six of them are preamp tubes, and the other small tube is the phase splitter. The PI is the one right next to the end power tube.

The rest of them are numbered in order starting from the input jack end.

You are going to wind up with a pile of perfectly good spare tubes.

I would have swapped places with tubes into V1. That is the input tube and should be the least noisy tube you can find. A tube that is hissy there will work fine as the PI or reverb tube, or most anywhere else in the amp.

V1A - input stage
V1B - Ch.1 gain
V2A - Ch.1 EQ recovery
V2B - Ch.2 gain
V3A - Ch.2 gain
V4 - Ch.2 EQ driver
V5 - reverb
V6A - loop recovery buffer
V6B - main preamp out buffer

[5150 TONE]

Thank you very much Enzo..I have several more questions for the forum.. Since only 5 of the 7 preamp tubes are working,where should I put the 2 tubes that are not working? Is it safe(for the amp) to switch the preamp tubes around with the amp on so I can hear if the noize is reduced with out turning the amp on and off ? Can I just leave the non working tubes out of the amp or should I leave them in a certain position in the preamp stage? What are the minumum amount of preamp tubes I can use in this amp (Ampeg VL-1002) and where do they have to be to run the amp safely? What are my options ? "V1A - input stage
V1B - Ch.1 gain
V2A - Ch.1 EQ recovery
V2B - Ch.2 gain
V3A - Ch.2 gain
V4 - Ch.2 EQ driver
V5 - reverb
V6A - loop recovery buffer
V6B - main preamp out buffer" Thanks again Enzo!! I have been searching the net for days trying to find out this information there is not alot out there about the VL-10002 except user reviews..Anyone else Please feel free to throw your expert opinions in. I am very excited to get this amp up and running to its full potential and would really appricate any help that you might give..Thank you.

[Enzo]

NEVER pull tubes when the circuit is powered. If it is just the heaters and the amp is in standby, well, OK, but don't do it with the high voltage on. It can make very loud noises out the speaker, it can spark at the socket, which can damage the socket pins and possibly start an arc.


There are no safety or reliability issues with leaving a preamp tube out. It just won;t work right. Leave out a tube and whatever its job was won;t get done. Looking at the tube list:
V1 - the input tube, serves both channels, so it must be there.
V2 - one half of it is used in each channel, if it is missing, both channels die. So it must be there.
V6 - is the output for the preamp, so it must be there.

Those tubes in place are enough to complete the channel 1 path. You could then leave out V3 and V4, those are only used in channel 2. Set the amp to channel 1 and see how the erst of the amp works. of course channel 2 won't function.

You cuold also pull V5 and the reverb would stop, but since you have two bad tubes, one of them would have to be part of channel 2 anyway, so might as well leave the reverb happening and pull the two Ch2 tubes.

[5150 TONE]

Thank you so much Enzo ..You have know idea how much I appreciate your help in this matter.. I am very grateful ...Just a note I think someone may have modified the circuts in this amp some where along the line because the 2 tubes that were not working originally were in V1 and V6 per your explanation of the tube stages and I put a spent tube in V5 and still had reverb today that is why I was asking for such an in depth explanation of the preamp stage in this amp.. If you are willing to share any more of your knowledge regarding amps since no one else has chimmed in yet that would be great.. I will do some more experimenting tommorow with the help of your advice and try to confirm my statements in this post..