70s Ampeg V4B Blows Fuses

[ca7922303]

V5,6,7,8-pin#8(0.00mv)

[ca7922303]

R201,202,203,204,206,207,18,19,20,28 still measuring resistance per schematic. No components appear burnt.

[vintagekiki]

V5,6,7,8-pin#8(0.00mv)

normally pin8 is the PT cathode that goes to gnd

[vintagekiki]

No components appear burnt.

In order for measuring instruments to serve their purpose, they should occasionally be made happy for their birthday with a modest gift.
The new batteries in the measuring instruments are a miracle.
They broaden the horizons.

[ca7922303]

Any thoughts on why I'm getting millivolts instead of volts after a loud pop near V5?

[vintagekiki]

Be more specific in describing the symptoms.
You are very stingy on words.
For V5 you asked a question, got an answer, what is the problem now.

About V5
#123

[g1]

One of the supply voltage dropping resistors may have opened up or have a bad solder connection.
These would be the voltages on either side of resistors R51,52,53, & 55.

[vintagekiki]

I guess he learned something from these 127 posts.
At least now knows that dmm requires the correct battery.
I regret the master who will take over the repair this "70s Ampeg V4B"

[ca7922303]

R51(2.2k), R52(OL), R53(OL), R55(0.46K) resistance. R51(570v/570v),R52(-4mv/570v), R53(585v/5mv), R54(585v/585v). When I replace R52 & R53 are they 2 watt resistors?

[ca7922303]

2nd measurements were DCV

[vintagekiki]

R51(2.2k), R52(OL), R53(OL), R55(0.46K) resistance. R51(570v/570v),R52(-4mv/570v), R53(585v/5mv), R54(585v/585v). When I replace R52 & R53 are they 2 watt resistors?

Yes R52 & R53 is 4.7k 2 watt resistors.
When measuring the voltage, in which position is SW₄

[ca7922303]

Actually now that i've flipped it over to component side, R52,R53 were never on this board

[ca7922303]

Also, not sure what is SW4?

[vintagekiki]

About R52, R53, SW4
Look at the schematics

For R52, R53, g1 wrote in previous posts ... I think these are sometimes mounted elsewhere, off the board ...
Browse the topic from the beginning.

[g1]

SW4 is the standby switch. It needs to be in 'play' position for all the testing. R52 and R53 are possibly mounted on the big capacitor cans. I'm not sure if you have your meter on the trace side of the board? You may have to dig in more with your meter to get the reading. Please re-check.

[ca7922303]

This resistor measures 620v/311v.