Cyrus 2 - V7 Roedensteins...

[ilimzn]

It will (should) show 0 (zero) Volts, because it is a symmetrical supply amp (no output capacitor, no DC voltage there), as mentioned before, that's why the cap needs to be bipolar.

The voltage and polarity of the cap do not have any direct relationship to the fact the amp has a dual voltage supply, rather with how the input stage is done, i.e. what direction the bias current for the input transistor base flows.
The voltage will however only be in the (tens of) mV range. Bipolars are still highly recommended as they generally outperform polarized caps in such circumstances, as they are made to work with any polarization across them, including none. Performance with no or little DC voltage across the cap, but with potential AC voltage, is what differentiates general purpose electrolytics from so called 'audio grade' ones. Even though general purpose ones will not suffer damage up to some half a volt or even more reverse voltage, there will be increased leakage current in that direction, i.e. a form of rectification, hence even order distortion will occur.

 

[audioIOguy]

Difficult to say as you show no circuit for the LED part.

Apologies - Here is the schematic. R119 and R120.

 

[EmpireAP1]

similar issues on my Cyrus 1

HI All

I had just wrote a fairly substantial post, that when i tried to submit i had to re-login and it binned it. I will CTRL-C this post.

I have a Cyrus 1 with a white noise hissing over the phono stage. Caps and voltage regs all sorted. Amp works on other inputs. Did the PSU checks and got 2v at the D13 and D16. Checked the diodes they give readings both ways. Could this be the problem?

Thanks

 

[Ian Finch]

That's a different amp. model, schematic and problem. Are you referring to the Cyrus 1 schematic which is slightly different? Cyrus 1 - Manual - Stereo Integrated Amplifier - HiFi Engine
I can't tell from your description what 2 points of measurement you mean when you say "....got 2v at the D13 and D16." Is that with respect to ground or across either diode or both? You need to be specific about what points you are measuring and in this case, I'm curious what you were looking to find there, reading the catch diodes at the output of one power amplifier. Is it the output level?

Were you listening to the amplifier with phono selected but no turntable/cartridge connected? If so, there will be plenty of noise (hiss and hum) since these are high sensitivity inputs for signal levels of only around 5mV on the MM input and even less on the MC input. With no input load, the noise will be quite loud but even with a turntable/cartridge connected, some low level noise, in addition to that produced by the needle on the record surface, will be generated by the phono preamplifier(s). This is normal for phono reproduction and will always be present at some low level, even with correct connections and set-up.

 

[EmpireAP1]

Thanks for the response Ian. I have just been retesting everything to start fresh but from that have discovered that my test leads are faulty so I was getting varying results. Need to go get some new test leads.

I appreciate they are different amps but do use the same circuit board. There are only a few differences. I have the manuals for the 2 and 1.

Thanks