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Old 5th Dec 2021, 12:26 pm   #42
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Join Date: Oct 2016
Location: Maldon, Essex, UK.
Posts: 151
Default Re: Taylor 65B Sig Generator: Dodgy Waveform

Originally Posted by HowardB View Post
What's the ac voltage across the anodes on your one?

I measured 194v at V1 cathode and 75 volts across R1 (194 - 119) which gives 7.5 mA.
How does this compare to your set?
I measured:
  • 161/160V a.c. at the rectifier anodes.
  • 194/187V d.c. and 6/7 V the rectifier cathode and one end of the 10 kΩ resistor between the electrolytic capacitors.
  • 137/117V d.c. and 0.4 V a.c. at the other end of the 10 kΩ resistor.
This is about 57/70 V across the 10 kΩ resistor which gives 5.7/7.0 mA. This increases to 63/73 V at the lowest frequency setting.

The first reading is switched to INT. MOD. The second reading is switched to EXT. MOD. C.W.

A photograph of the mains transformer secondary connections is below for you to compare. I think that the black wire is the screen and is connected to ground. One of the two pink wires is connected to ground and other goes to the anodes of the rectifier (My anodes are connected together). One of the top two wires with the red sleeve is connected to ground and the other is connected to the rectifier pin 7 for the heaters.

The electrolytic capacitors would be prime suspects if mains hum is a problem. However, you stated in post #1 that you have replaced the usual caps.

As can be seen in the photographs, I replaced the electrolytic capacitors and waxed paper capacitors except the one connected across the heater supply. Itís awkward to get at and at 6.3 V a little bit of leakage is not going to matter. I did not change the flat rectangular waxed mica capacitors. These are unlikely to be defective and any change would alter the calibration.

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