magnavox 185aa with 4-6v6

[tim614]

anyone have info on this magnavox console amp model 185aa
it have four 6v6 one 5u4 two 12ax7 and one 7025 for phono input

[GordonW]

I've rebuilt lots of these. Whaddya need?

Schematics can be found over in Yahoo Groups- at the MagnavoxFriends group.

Those amps are quite nice, once they're updated. Key things are, IME, to replace the cathode bias cap on the output tubes (this is a first order of business for me, seeing how many of these caps have gone bad and caused WEIRD behavior out of the amps), replace the input coupling caps (to and from the 12AX7 tubes), and IF you want to use the AMP185 as a stand-alone power amp (out of the console), disabling and removing the phono input circuitry (which involves removing the 7025 and rewiring the amp so that the signal from the RCA input jacks goes directly, through a coupling cap, to the input grid circuit of the 12AX7 for each channel.

If you want to do this changeover (removing the un-needed phono stage), the easiest way is to just use the Magnavox AMP175 circuit- it's the same exact amp as the AMP185, just MINUS the phono stage (i.e, no 7025 or associated circuitry). IIRC, that schematic is also available over at MagnavoxFriends on Yahoo Groups...

One other helpful mod, IME, is to disable and remove the "balance pot" that was factory-installed on one channel. On these amps, the two channels are wired slightly differently... one has slightly more gain, and the balance pot (to allow it to be adjusted to gain-match the other channel, to compensate for the pretty variable speakers of that era, in the original consoles). In this day and age, it's better to EXACTLY MATCH the channels... to do this, just re-wire the channel with the balance pot- remove the pot, and change everything over to where all the wiring and component values MATCH the channel that DID NOT have the balance pot...

There's other stuff you can do (bypass caps, etc), but these are the big things, that most people wind up doing...

Regards,
Gordon.

[tim614]

do you have any picture of some you done? i would like to see in detail if i can specialy under the hood ,visual are best for me
i do have the schamatic from the yahoo groop but im still new at this .i just finish a 9302 model by looking at deferent picture and schamatics on the yahho groop and on here .
if you dont mind i will very apreciated.

[jaymanaa]

I would be interested in knowing the differences in the 175 and 185 circuits. I've always used the 175 circuit which utilizes 12AX7s up front.