Fender M-80 Bass Schematic

[dcktech]

Hi,
Just signed up and am currently working on a M-80 Bass Amp. I see there is lots of discussion on it. Just wondering if anyone has a Schematic for it.
Thanks

[teemuk]

http://www.mif.pg.gda.pl/homepages/tom/files/FenM80.gif

[dcktech]

m-80 bass schematic

Thanks for the schematic - Teemuk
Dan

[dcktech]

Fender M-80 Bass Schematic?

Hi,
The schematic I recieved is not correct.
My model is Fender "M-80 Bass"
PR 178
Ser# LO-494616

Does anyone have any other schematics specific to this model?

Thanks,
Dan

[icefloe01]

Fender has ordering information here: http://www.fender.com/support/manuals/manuals.php and it looks like the four different M-80 products would be $5.00 each if no one here has one in their archive...

Eric.

[Enzo]

WHO sent you the wrong one? And did you ask specifically for the M80 Bass? As ice says, there are several M80 amps.

[teemuk]

Here's one to revision B:
http://www.mif.pg.gda.pl/homepages/tom/files/FenM80.gif

[dcktech]

M-80 Bass Schematic Pwr Section

Hi Guys,
the schematic i received has a different power section than what is actually on the board.
According to the schematic CR49 & CR50 are Zerners - controlling the +16V and -16V.
On the board are 2 regular IN5402's diodes.
Now as far as the voltages I have only +6.6V (on CR49) and -16V (on CR50).
I susspect this is the problem, since I need +16.

Any Ideas?

Thanks,
Dan

[oc disorder]

Thats weird...I thought all the M-80's used zeners.
I would double check them .. one end should connect to a large oblong
whiteish wire wound resistor 5 watts or 7 watts 270ohms or in some guitar amps 330 ohms.
In fact there was a fender tech bulletin for the bass amp in '93

M-80 Bass Power Supply Modofications
A resistor change is required in the power supply section to reduce the amount of current through the 16 volt zener diodes CR49 & CR50. This will minimise the possibilty of the zeners overheating.
Remove R144 & R145 (270 ohm, 7W), and replace them with 390 ohm, 7W wire wound resistors. Make sure to glue the resistors to the p.c. board using an RTV silicone compound.

[Enzo]

They say 1N5402 right on them? Right nexst to each other in the middle along the edge of the board? They are 5 watt zeners, so they look like 3A rectifiers. But they should be 1N5353. Change the one that reads 6 volts, they should show 16v.

[dcktech]

Fender M-80 Diodes/Zerners

Hi guys,

OK I think I finally got to the bottom of this. The other Night I only removed CR49 and it was the IN5402. Which did not match the schematic. I SHOULD have removed CR50 - never assume! Of course CR50 was correct (IN5353B). Then I pulled out CR35 - it had some obscure diode in there so I put the IN5402 from CR49. I will get another IN5353B tomorrow and put it all back together.
I have no idea where this guy had this thing serviced - but they really screwed it up.
I will keep you posted on how it sounds after this.

Thanks,
Dan