Hacker Cavalier Loud Noise

[peter_sol]

Is there nobody near to Martin who could look at this with him?
Yes one of the valves makes cracking noises and needs replacing but there are other man made problems now.

[Edward Huggins]

Look, all of this has been going on for far, far too long. I can see you soldering and then re-soldering ad finitum. Why not get someone from from in, or around, Sheffield to give this a look over? It will put you out of your misery and let you enjoy your player. There's no disgrace in having some hands-on help! Edwad

[Station X]

Originally Posted by martinpinner

If replacing valves. Is it correct that you have to purchase a matching pair.

Don't even think about replacing the valves until you've sorted out the other problems. No point in wasting money unnecessarily.

Getting local help would be good, but I think Martin is nearly there.

Resoldering R6 should result in HT voltage being present on the triode anodes of both valve holders (pin 9).

We can take it from there.

[martinpinner]

I need to replace R3 as it only reads 0.77. I have located a 2.2m resistor but only 0.5W rather than 2W that I normally buy.Is this OK?

[Station X]

Originally Posted by martinpinner

I need to replace R3 as it only reads 0.77.

0.77 what? We need units!

R3 is a 2.2 Mohm resistor. It would be extremely unusual for it to go low in value. Its colour code should be Red, Red, Green. Have you checked it out of circuit? You only need to disconnect one end. Unplug the valve too, just in case. With the resistor disconnected you should see infinite resistance from pin 1 to chassis.

[Lucien Nunes]

I think that should say red/red/green!

[Station X]

Correct. I've edited my post.

[Station X]

Here's a picture taken from an earlier post.

The resistor "squared" in red is probably R3. Lower end goes to pin 1?

The resistor lead "squared" in blue looks like it may be touching the centre spigot of the valve holder and needs to be cut back.

Note that as this is an early picture, some wiring is shown incorrectly.

[martinpinner]

Thanks again.The reading is 0.77Mohms.With regard to having someone look at the player I would like to try and complete this myself.Having said that I am very grateful tor everyone help in getting me this far. It has been very much a "learning curve" for me and probably frustrating to you all. Dare I say I think I am beginning to understand the circuit diagram.

[Station X]

If R3 tests as 0.77Mohms (770kohms) in and out of circuit, with the valve unplugged, then it has gone low in value.

A 0.5W resistor will be fine in this position.

[julie_m]

0.77 MΩ is equivalent to 770 kΩ and is well out of tolerance for a nominal 2.2 MΩ resistor. (Thought: You weren't holding the test probes in place with your bare hands, were you? There would be no danger of a shock as long as everything was powered off except the multimeter, but your body resistance could have spoiled the reading.)

Realistically, there is not much chance of anything dissipating more than a few milliwatts in a resistance of 2.2 MΩ. A physically larger resistor would be able to withstand a greater applied voltage, but that is very unlikely to be a problem in a record player. (Maybe in a guitar amplifier, with high HT.) A 0.5 watt part will be fine; although it may look out-of-place among older, physically larger parts. (If I was entering an art exhibition, I would use all new one-watt metal-film resistors, spaced perfectly central on the tag strip, and all with their tolerance bands at the same end ..... actually, even if I just screwed the lid back on and tried to forget about it, it probably would still keep gnawing away at the back of my mind .....)

[martinpinner]

Thanks. Should I be wearing gloves when testing components as I always just hold the probes in my bare hands.

[Station X]

When measuring resistance there's no need to wear gloves. Just don't touch the tips of the probes or croc clips as the resistance of your body will affect the reading, especially where high value resistors are concerned.

[Nickthedentist]

Yes, just hold the PLASTIC bits of the test prods, not the metal tips.

[martinpinner]

I just disconnected R3 from pin 1 and tested it in and out of circuit and now have a reading of 2.4 Mohms. I believe this is within tolerance and will leave in place.

[Station X]

It is indeed in tolerance, but I am puzzled as to how it measured 0.77Mohm when in circuit. Either your measuring technique was at fault, there is/was a wiring error or there is an inter-electrode fault in the valve.

If with the valve plugged in and the resistor fitted, you measure 2.4Mohms from pin 1 to chassis, then all is OK.

[martinpinner]

R3 is now in circuit and with the valve fitted the reading is again 0.78mohms. If it is a wiring error what is the best way to try and identify. It also gives a reading of 0.78mohms without the valve fitted.

[peter_sol]

If you unplug the input plug which leads to the volume and tone control, you then have one end of R3 to chassis line only and other end to valve grid only.

See if it varies when plug in or out.

[Station X]

I think we may be chasing a none existent fault here. A note on the diagram says that C15 is only fitted to the GP15ST version. For the player to work, C15 would have to be replaced by a short circuit, which would put C3 in parallel with the volume and tone controls. This would result in R3 measuring low when in circuit.

A simple check for this is to measure the resistance across R3 whilst turning the Vol and tone controls. If the resistance then varies, then C15 is not fitted.

[martinpinner]

I presume that the "input plug" are the two spade connections.There is no difference in the reading whether plugged in or not.With regard to C15 I read on the circuit diagram that C15 is not required on the GP15ST. When checking R3 whilst turning vol/tone(player switched on) the resistance varies. Having done that the reading is now consistently 0.18mohms..