The Amp Garage

Sorry - I did not catch your last line untill I posted the above. This is in fact boogafunk that you are allready aware of

Randy

Check out this ebay link for an unfinshed theil ported cab - I think this guy has them available most of the time

http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWAX:IT

Randy

"T" on the preamp section should connect to ground below R21 10K tail resistor. Actually I think C14 should be dawn on the preamp section as it belongs with the PI. With "T" wired as you have it drawn your master vloume pots are 10k abouve ground and floating on the PI bias network. We dont have a p...

After rereading the entire thread my best guress is that there was a bad solder joint at the junction of the 22k,1k5 and the wire going to the cathode and you never had NFB working. These little amps sound good with NFB or with out. When the owner resoldered the wire it let the 22k make contact for ...

When the NFB circuit is hooked up it oscillates. That means the phase is positive not negative. A resistor will not alter the phase so forget the 22k as suspect . You could hook 3 caps up in series and get it going positive as a cap causes a 60 degree phase shift. Thats why you find 3 in trem circui...

What you have done is remove the negative fedback and that stoped the oscillation. the big queston is what made it start oscillatioing or was it always doing it. You can swap the OT primary leads and hook the 22k back up and see if it has stopped. I dont think the resistor if failing as there is not...

I believe that a PM does stay in your out box until the recipeint opens it.

Randy

Your are not starting with 600 volts. Your tansformer is a 300-0-300 CT and you are rectifing each 300 volt section twice per cycle (that's where 120hz ripple comes from). In theory with no load the 300 volts should charge up the filter cap to 1.414 times the 300 volts which equals 424 volts. If you...

Hello Steve
Very nice build all around - Looks and sounds fantastic.

I would like to know what the PT and OT specs are if its not too much trouble.

Thanks Randy

I think you guys are reading way to much into his add copy. I did a search on that page and only twice did I find "trainwreck" and that was "has a classic rock voice similar to a vintage Marshall or Trainwreck™".... to my mind that is along way from "Trainwreck Inspired". Infact Marshall comes first...

Wjdunham wrote: Thanks Randy. It's easy enough to swap the OT primaries and see what happens. I'm a little unclear at to your first point though. I checked to make sure the actual was wired like the schematic (ie, that there wasn't a wiring problem when fender built the amp), and that I connected m...

I just looked at a schematic for the prosonic and sure enough - no NFB. Saying that it is wired correctly from pictures and schematics is a moot point in this case as you have no point of reference of a circuit working with NFB. It could just as likely that the OT is wired so that you NFB is in phas...

I dont believe the layout is for that schematic. It looks like the layout is for an amp with a cathode follower and HRM and has 100K plates on V1. The schematic doesnt indicate any of those items. Correct me if i am wrong.

Regards
Randy

Marshall used a voltage doubler in some of the 100 wat amps.


Check this discussion at metroamp forum:

http://forum.metroamp.com/viewtopic.php ... 46d5f3784f


Regards
Randy

The cap in the HI CUT circuit (C11) is marked as .022uf. The Rocket and VOX schematics indicate .0047uf. If you have changed the value, how has it workrd out?

Thanks
Randy