Murphy A851G no sound to speakers. Tone arm fault on Garrard deck.

[ms660]

I'd replace the rectifier, you said you had the parts to do so.

Lawrence.

[Gazworth]

Originally Posted by ms660

I'd replace the rectifier, you said you had the parts to do so.

Lawrence.

Done! now getting 185v through out. i can now hear an audible buzzing noise from it. hopefully this is it.

sorry for the ropey work so far it will tidy it up haha.

also can i just say thanks so far to everyone, very new to these older circuits and im learning alot so thank you

[Gazworth]

well progress is progress is suppose, all voltage are now good, getting around 185v DC on both inputs to the valves, they heat up nicely. still no sound though when playing a record. i have changed the cartridge as i was instructed to but im not certain its a good one. either that or ive done it wrong haha.

[Edward Huggins]

That re-wiring is a fiddly job. To double check the efficacy of this, do the Buzz Test again by touching the pins inside the female bayonet cap at the end of the tone arm and see if there a signal. If there is, I would suspect the cartridge rewiring. Edward

[PaulR]

Is the voltage you mention on the anodes of the ECL86(s) pins 6 and 9? Also is the noise you hear coming from the speaker itself?

[Gazworth]

Originally Posted by PaulR

Is the voltage you mention on the anodes of the ECL86(s) pins 6 and 9? Also is the noise you hear coming from the speaker itself?

Checking the schematic yes thats correct

[Gazworth]

the buzz test isnt working, so im lost now again. i can hear a buzz fro mthe speaker section but its a low buzz. just no feedback when carrying out the screw driver test.

[Station X]

Please check all voltages and compare them with those shown on the circuit in the service manual.

https://www.service-data.com/product...77/5162/m19977

[Gazworth]

pics of voltages so far .

[PaulR]

Can you touch the centre tab of the volume control? You might have to use a screwdriver if it is inaccessible. Be careful not to touch the mains tabs if it is a switched volume control.

As Graham suggests the way forward is to post a list of the valve pin numbers and the voltage on each. Don't leave it running for long, particularly if the valves are getting very hot.

[Station X]

Originally Posted by Gazworth

pics of voltages so far .

What point are you measuring in the first picture?

Second and third pictures show tests on smoothing capacitors which is fine.

I assume pictures 4 and 5 are the anode voltages on the output valves? In picture 5 it's not possible to see where the probe is probing.

Best to post valve pin numbers and voltages.

[PaulR]

You are probably going to need 3 x 0.01 capacitors like these https://www.ebay.co.uk/itm/Vishay-MK...wAAOSweotf9gj8

but let us know the voltages first

[Gazworth]

Apologise first of all for my lack of knowledge, secondly for my writing and thirdly if im not aloud to post the schematic pic then again sorry.

these are the voltages ive managed to pull up.

i hope this is more clear.

thank you guys!

[PaulR]

We are not supposed to post the entire circuit diagram as they are available from this site for a small fee which helps to pay for the upkeep of the site.

Anyway, I think you must be referring to the pentode output sections of V1 and V2 which are V1b and V2b. If you really have over 100v on pin 9 of these that is where your fault lies. The control grids should have a small negative voltage on them. If correct the voltage you see is there because the coupling capacitors are leaking badly. Others on here are much more experienced than me but I find it surprising that those voltages are so high because pin 9 of V2b is protected by two capacitors, C5 and C7. Having said that you also have a high voltage on pin 3.

Can you double check the voltages? I think you should change C5, C7 and C8 whilst you are in there.

[ms660]

Originally Posted by PaulR

If you really have over 100v on pin 9 of these that is where your fault lies.

Pin 9 is the anode of the triode.

Lawrence.

[Station X]

Pentode sections look OK to me.

Pins 6 anodes c 208V
Pins 3 screen grids c 184V
Pins 7 cathodes c 5.4V

No readings for pins 8 control grids though. Please confirm that these are close to zero volts.

[Techman]

Originally Posted by PaulR

I think you should change C5, C7 and C8 whilst you are in there.

These don't need any capacitor changes as they use high quality ceramic types for the two grid couplers as original factory fit - I've not checked against the circuit, but I guess that's what you mean by C5 and C7 or 8? However, it's worth just checking for positive grid volts just in case, and if it's found that there is, then it's more likely to be caused by grid emission of the valves themselves.

Just skimming through this thread I can't believe all the unnecessary component changing that's been done, possibly causing man made faults that weren't there before. Pretty much the only thing that ever goes wrong with these players is the rectifier. If HT voltage had been checked first and the rectifier replaced with a diode and series resistor it would probably be up and running by now - there's been enough previous thread posted about this problem over the years.

Edit to say - you can see the high quality disc ceramic capacitors in the second photo in post #10.

[Station X]

Triodes good too.

Pins 9 anodes. V1 127.6V V2 159.4V
Pins 2 cathodes V1 1.24V V2 27.17V
Pins 1 control grids V1 0V V2 16.05V

Not spot on, but shouldn't stop player from working.

Try a buzz test at the centre tag of the volume control.

[Station X]

Originally Posted by Techman

If HT voltage had been checked first and the rectifier replaced with a diode and series resistor it would probably be up and running by now - there's been enough previous thread posted about this problem over the years.

I've never understood why some people reach for the soldering iron before reaching for their meter.

[PaulR]

Originally Posted by ms660

Pin 9 is the anode of the triode.

Lawrence.

Sorry I was looking at the circuit diagram which uses ECL83s