Ampeg rocket 2. i need help from experienced guys!!!!!!!!!!!!

[Bmxbarspin724]

i have an ampeg rocket 2. one of my friends was playing it one time, and it just stopped working. i looked at the tubes, and 2 tubes needed to be replaced. the tubes were 7199 and 12AX7. i replaced the 7199 tube with a 6AN8A, and i replaced the 12AX7 with a ECC83. the 6AN8A is an audio tube i think, but i heard you could use it to replace a 7199, and it was 30 dollars cheaper.

now when i turn it on, it turns on fine. its quiet then it hums up a bit, then it dies down. i assume this is just the tubes warming up.

the problem is, no matter how loud i turn up the volume, i cant get any sound out of it. i know the speaker is hooked up because if i press my finger against the end of the cord, where it plugs into my guitar, it buzzes like electricity.

could the problem be the substitute of the 6AN8A for the 7199 or is it a bigger problem?

any help would be apreciated.

[Bruce / Mission Amps]

i have an ampeg rocket 2. one of my friends was playing it one time, and it just stopped working. i looked at the tubes, and 2 tubes needed to be replaced. the tubes were 7199 and 12AX7. i replaced the 7199 tube with a 6AN8A, and i replaced the 12AX7 with a ECC83. the 6AN8A is an audio tube i think, but i heard you could use it to replace a 7199, and it was 30 dollars cheaper.

now when i turn it on, it turns on fine. its quiet then it hums up a bit, then it dies down. i assume this is just the tubes warming up.

the problem is, no matter how loud i turn up the volume, i cant get any sound out of it. i know the speaker is hooked up because if i press my finger against the end of the cord, where it plugs into my guitar, it buzzes like electricity.
could the problem be the substitute of the 6AN8A for the 7199 or is it a bigger problem?

any help would be appreciated.

I'll have to look but I don't think a 6AN8A is interchangeable with a 7199 at all... they might be similar tubes in design concept but I don't think they have the same pinout.
I think you have to rewire the socket.
***************************************

I just looked at my tube chart ... I'd take that 6AN8A tube out asap! Go get the right one and hopefully you didn't damage the B+ rail with a short somewhere.

[J Martin]

Right, those tubes do not have the same pin out. You need to rewire the tube socket or cut and jumper if its a PC board.

How could you tell the tubes were bad by looking at them? I wish I had that ability, it would save a lot of time.

[Bmxbarspin724]

oh thank you. how would i tell if i damaged anything? and is there any other tube that will work as a 7199?

and could i, as an amatuer, rewire what i need to rewire?\

and as far as telling that the tubes were bad, they didnt light up, when i turned the amp on. its pretty easy.

[J Martin]

Just so I don't make a mistake, I will type the conversion instructions in the back of Pittman's TUBE AMP BOOK.

Do not alter pins one, four, or five.
move connection on pin two to pin six
move connection on pin three to pin seven
move the wire that was on pin six to pin nine
move wire that was on pin seven to to pin eight
move wire that was on pin eight to pin three
move wire that was on pin nine to pin two

It might be easier if you remove all wires first, but be sure to label them.
You can look at any online tube reference to see that connections are made correctly to corresponding elements of the 7199 and 6AN8. There is no direct substitute for the 7199 that I know of. New Sensor had one a few years ago, but I was told it was just a repinned 6BL8. It worked ok in some circuits but sounded horrible in others. (like old Ampegs) I have done this operation a few times and the sound is not degraded in any way in guitar amps. If I were building an amp with this topology, I would use an EF86 or 6AU6 and a 6C4 individual pentode and triode. Any damage would likely show as a burnt resistor, but I dont have the circuit in front of me.

[jrfrond]

New 7199's are available from E-H. Why even hassle with the rewire?

[Bmxbarspin724]

E-H? what is that? excuse my noobiness.

[J Martin]

Unless New Sensor (EH) has changed the design, I wouldn't put them in an old Ampeg. Experiance has shown they perform badly in those amps.

[Enzo]

EH is Electro Harmonics, one of New Sensor's tube brands.