Please help me out. 1969 100w build

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no0sand1s
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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sat Jun 02, 2018 2:35 pm

Good day, gents.

updated voltage chart/notes from reconnect: https://www.flickr.com/gp/wedinbordeaux/AUrb45

One green wire was open, the other about 6 ohms (I used this for ground) when connecting the heater wires. I read 3.49VAC at heater connections for each socket.

I read -50VDC (not AC) after wiring bias wire at pin 5 for each output tube.

HT wires connected to standby switch - I read 179VAC at each connection to the switch.

see enclosed photos for each connection to each point.

fuses checked, neither are open

voltage chart enclosed - for input tubes, pin 4, 5, 6 are 3.49VAC, 0VDC. all other readings are VDC

thanks for looking!

Tazin
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Re: Please help me out. 1969 100w build

Post by Tazin » Sat Jun 02, 2018 4:51 pm

OK, so it looks like the heater voltage (Vac) is good now on all tube sockets although it is a little high. Also, the bias voltage (Vdc) is good at pin #5 on the output sockets. So, the only problem you have now is with the H.T. voltage after rectification since the secondary winding on the PT is putting out the correct ac voltage (179Vac) on both the Blue wire w/white stripe & the Gray wire at the Standby switch. If you haven't done so already double check the H.T. Fuse with a meter to ensure that it is good. You could have a bad diode in the bridge rectifier (overheated from soldering) so if your multimeter has a diode check function you may want to test each diode in the bridge rectifier. I'm not sure if a bad snubber cap (0.22uF/1000Vdc) would cause a problem like this.

no0sand1s
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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sat Jun 02, 2018 5:03 pm

I used a meter to check the fuses - they both show continuity. The voltage readings were read with the standby switch in the 'off' position.

I removed/tested all 5 diodes. I get OL in one direction, and 0.58VDC, reversed, so they're good.
Last edited by no0sand1s on Sat Jun 02, 2018 5:38 pm, edited 1 time in total.

Tazin
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Re: Please help me out. 1969 100w build

Post by Tazin » Sat Jun 02, 2018 5:32 pm

You should be able to test them without removing them from the circuit.

no0sand1s
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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sat Jun 02, 2018 5:39 pm

I removed/tested all 5 diodes. I get OL in one direction, and 0.58VDC, reversed, so they're good. snubber caps removed, tested at .22K.

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Re: Please help me out. 1969 100w build

Post by Tazin » Sat Jun 02, 2018 7:56 pm

So, what's the dc voltage at the output of the bridge rectifier?...It will be where the Red wire connects.

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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sat Jun 02, 2018 8:04 pm

0.03VDC.

Tazin
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Re: Please help me out. 1969 100w build

Post by Tazin » Sat Jun 02, 2018 9:14 pm

If I'm not mistaken the Red wire at the output of the bridge rectifier connects to the H.T. Fuse, so pull the fuse and recheck the dc voltage at the output of the bridge rectifier. Also check the ac voltage at each Blue wire where they connect to each 0.22uF/1000v snubber caps near the bridge rectifier...Hopefully you'll have that 179Vac at each Blue wire.

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neikeel
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Re: Please help me out. 1969 100w build

Post by neikeel » Sun Jun 03, 2018 8:36 am

Tazin wrote:
Sat Jun 02, 2018 9:14 pm
If I'm not mistaken the Red wire at the output of the bridge rectifier connects to the H.T. Fuse, so pull the fuse and recheck the dc voltage at the output of the bridge rectifier. Also check the ac voltage at each Blue wire where they connect to each 0.22uF/1000v snubber caps near the bridge rectifier...Hopefully you'll have that 179Vac at each Blue wire.
:thumbsup:
Neil

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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sun Jun 03, 2018 11:58 am

Correction: -.031 VDC at red wire.
Each blue wire shows 0 VAC.

Tazin
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Re: Please help me out. 1969 100w build

Post by Tazin » Sun Jun 03, 2018 12:26 pm

Huh...Just to make sure were all on the same page here...
All the mains transformer wires are hooked up; correct?
The amp was not in Standby mode when you were taking the ac and dc voltage readings; correct?
If the answer is Yes to the above questions then try this...Leave the H.T. Fuse out and check the ac voltage at the Standby switch (in Standby mode this time) for the Gray wire and the Blue wire with the white stripe. Once again hopefully you'll see that 179Vac at each wire.

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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sun Jun 03, 2018 12:40 pm

My standby switch was off. I turned it on, and I get 180 VAC at each for the blue wires on the rectifier. With the fuse in , standby turned on, I now get 496 VDC at the rectifier output. My output tubes are not yet installed.
Last edited by no0sand1s on Sun Jun 03, 2018 1:27 pm, edited 1 time in total.

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Re: Please help me out. 1969 100w build

Post by Tazin » Sun Jun 03, 2018 1:07 pm

All right then...Those are the voltages we were looking for. So, just to recap:
The heater ac voltage on Pins #4, #5, #9 on the preamp tube sockets is 3.49Vac; correct?
The heater ac voltage on Pins #2 and #7 on the output tube sockets is also 3.49Vac; correct?
The dc voltage at Pin #5 on the output tube sockets is negative 50Vdc; correct?

If the answer to the above questions is Yes then it's time to redo the voltage chart so we can see what the voltages are for the entire amp once again. So, with the output tubes removed (preamp tubes installed) and the H.T. Fuse installed along with the amp in "play mode" create a new voltage chart. Hopefully your voltages throughout the amp will be close to what George's base-line voltages are.

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Re: Please help me out. 1969 100w build

Post by no0sand1s » Sun Jun 03, 2018 2:47 pm

the metro assembly instructions stated to leave the standby 'off', so it was never on during my previous voltage readings.

here's a link to voltage chart results: https://www.flickr.com/gp/wedinbordeaux/V49ipa

everything looks great, except I lost -50 V @ pin 5 of each output tube location. I checked the bias wire voltage where connected to the turret board and read 99 VAC.

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neikeel
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Re: Please help me out. 1969 100w build

Post by neikeel » Sun Jun 03, 2018 4:40 pm

Tazin wrote:
Sun Jun 03, 2018 1:07 pm
All right then...Those are the voltages we were looking for. So, just to recap:
The heater ac voltage on Pins #4, #5, #9 on the preamp tube sockets is 3.49Vac; correct?
The heater ac voltage on Pins #2 and #7 on the output tube sockets is also 3.49Vac; correct?
The dc voltage at Pin #5 on the output tube sockets is negative 50Vdc; correct?

If the answer to the above questions is Yes then it's time to redo the voltage chart so we can see what the voltages are for the entire amp once again. So, with the output tubes removed (preamp tubes installed) and the H.T. Fuse installed along with the amp in "play mode" create a new voltage chart. Hopefully your voltages throughout the amp will be close to what George's base-line voltages are.
:thumbsup:
Neil

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