I'm in need of a schematic for an Ampeg b4r

[Garydean]

"""""Secondaries all measure good except for 1 (the >20 M ohm). """"

I didn't see the M after...

[Garydean]

If you run the amp on half power and connect the speaker to the 8 ohm jack you should be fine.

you may get a few different answers on this

[Garydean]

what you're doing there is measuring half...but not really...of the windings resistance to the centertap, which sounds ok. Can you measure the secondary to...

[Garydean]

Replace the fuse and turn on the amp without the rectifier tube in place. If the fuse still blows, the rectifier tube is not the problem. Perhaps one of your...

[Garydean]

thank you

[Garydean]

Are you sure you are measuring with your meter set to DC volts?
Yes measure to chassis.
I would remove the fuses and test them with your ...

[Garydean]

Here is the symptom.

Power-up
12 seconds before the fan starts;
38 seconds ( this time) before the sound starts
(26 seconds...

[Garydean]

Up for discussion.

Equipment.

Marshall 5210 1x12 (4ohm) combo SS 50W. Extension jack installed with a switch to select internal...

[Garydean]

I get this question all the time. I know it depends how much someone is willing to spend and what kind of music and how big the venue and so on and so on.........

[Garydean]

It's possible those output tubes are mismatched. Swap them and see what happens.

[Garydean]

Does the chirp volume increase when you turn up the volume? (not the master) Just want to be sure I'm reading it correctly. If so then your problem is in...

[Garydean]

First thought is the pre amp tubes. Check your new solder points then move some wires around in the preamp section. Sounds like oscillation perhaps from wire...

[Garydean]

Be sure the 3rd tube from the right, looking at the back, is a 12AT7 and the
4th tube is a 7025 followed by a 12AX7 then a 12AT7. Swap some tubes...

[Garydean]

I have an Eico cap tester....very old school as well. . Your model's schematic and user manual is going to be hard to locate. I'm sure it works like all the...

[Garydean]

Yes Knight made the KnightKit R/C Tester Model 83y124. They also used the Magic Eye.

gary

[Garydean]

Nice!! Glad to hear everything is working again.

Gary

[Garydean]

+1 Bob..... that was truly a genuine statement and very heart warming.

[Garydean]

Regis, sorry to hear about your misfortune. The silver lining in this cloud may not be apparent right now....but it's there. I would certainly start teaching....

[Garydean]

Also test those filter caps C35, C36, C37. Give the amp a smack on top and listen for any changes that could indicate a broken solder point. The circuit board...

[Garydean]

The original OT should be a 125A6A. They are not very beefy which is why you may think it's been replaced. Although, because of it's size many have been...

[Garydean]

"Motorboating" is what you're hearing. Low frequency oscillation is usually a symptom of a bad decoupling capacitor between stages. There could...