PYE Blackbox four speaker

[Techman]

Having worked on these, the only capacitors that you'll really need to replace are the four paper types C6,7,9,10. You might want to also replace C11, which is the output stage cathode decoupler and is the Plessey one that you mention. I haven't actually found any problem with this type myself in record players in general, including the Pye BB, but they are known to be very unreliable in other applications where they're probably more stressed, such as in older TVs. Always replace with nearest preferred modern equivalent value, at or a little above the stated working voltage, but never below.

You won't need to replace any other capacitors unless you have mains hum, or the main smoothing can starts to get warm after a short time - keep checking it and it would be a prudent idea to give it a bit of a chance to do a bit of reforming by using a lamp limiter, but only after you've replaced particularly C9 & 10. You can go round all the resistors with your meter to check for any that are significantly out of tolerance - you may find the cathode resistor, R25 (that's the one connected across that Plessey capacitor) has risen in value, perhaps just a little, but possibly by a lot. One thing for certain is that it doesn't want to be in close contact with that capacitor, as they always seem to have been when fitted by Pye - very bad practice, but they're all like that.

[Techman]

I'll make this another post rather than edit the last one in case you miss it, as I've left out the most important thing to check before going any further, and that is to check the continuity of all of the primary winding of the output transformer, as these are a known weakness if someone has previously run it with leaking capacitors C9 & C10. If one half of the winding is open circuit, as it sometimes is, then it'll need a professional rewind.

[nicam49]

Hi, just Google 'ecc82 datasheet'

[Techman]

Originally Posted by nicam49

Hi, just Google 'ecc82 datasheet'

Why does he need to Google the ECC82 datasheet? I don't understand the significance of this, unless I'm missing something, please elaborate

[RoyceVM]

I will check the primary windings for continuity. Thanks for the great advice.

[RoyceVM]

Originally Posted by Techman

Why does he need to Google the ECC82 datasheet? I don't understand the significance of this, unless I'm missing something, please elaborate

In the valve split diagram on the schematics, I found it hard to understand the valve pin order in the direction (forgot it was clockwise or anti clockwise 1, 2, 3....) and identify each viewed from the lower part of the chassis. I am trying to identify the valve pins which is which like on each of V1A and V1B -1/2 ECC82, V2A and V2B-1/2 PCL83, V3A and V3B-1/2 PCL83. Once I know that I can follow the pins and identify the paper caps and its value. I also like to know the voltages on those valve pin numbers.

[RoyceVM]

Originally Posted by Techman

Having worked on these, the only capacitors that you'll really need to replace are the four paper types C6,7,9,10. You might want to also replace C11, which is the output stage cathode decoupler and is the Plessey one that you mention. I haven't actually found any problem with this type myself in record players in general, including the Pye BB, but they are known to be very unreliable in other applications where they're probably more stressed, such as in older TVs. Always replace with nearest preferred modern equivalent value, at or a little above the stated working voltage, but never below.

You won't need to replace any other capacitors unless you have mains hum, or the main smoothing can starts to get warm after a short time - keep checking it and it would be a prudent idea to give it a bit of a chance to do a bit of reforming by using a lamp limiter, but only after you've replaced particularly C9 & 10. You can go round all the resistors with your meter to check for any that are significantly out of tolerance - you may find the cathode resistor, R25 (that's the one connected across that Plessey capacitor) has risen in value, perhaps just a little, but possibly by a lot. One thing for certain is that it doesn't want to be in close contact with that capacitor, as they always seem to have been when fitted by Pye - very bad practice, but they're all like that.

Great advice! Thanks so much! I really appreciate it.

[Edward Huggins]

Doesn't that under-chassis wiring look terrible in Post #15! The Girls cussed about these. Not only are the components so close together horizontally, they were stacked on top of each other. There was plently of room within the cabinet for a much larger chassis.

[nicam49]

Originally Posted by Techman

Why does he need to Google the ECC82 datasheet? I don't understand the significance of this, unless I'm missing something, please elaborate

Yeah, the circuit diag he has got doesn't have the pins numbered. The datasheet will help him solve it.


Royce, remember that the pins are numbered clockwise as you view them from underneath, starting at the gap.

[RoyceVM]

Originally Posted by RoyceVM

I will check the primary windings for continuity. Thanks for the great advice.

There are 4 pins. Only the two middle ones had continuity


1 and 2 had 66 ohms
2 and 3 had 38 ohms
3 and 4 had 85 ohms
1 and 4 had 189 ohms

Secondary had continuity but no resistance.

[RoyceVM]

Some additional pics of the transformer area

[RoyceVM]

Originally Posted by nicam49

Yeah, the circuit diag he has got doesn't have the pins numbered. The datasheet will help him solve it.


Royce, remember that the pins are numbered clockwise as you view them from underneath, starting at the gap.

Thanks so much! Now I remember! Unfortunately, those split valve diagrams have no pin numbers.

[Techman]

Originally Posted by RoyceVM

There are 4 pins.

Secondary had continuity but no resistance.

If you look at your circuit diagram that you posted you will see that there should be 5 connections to the primary. I think the readings that you've posted so far are ok, but the important one is to take a reading between the two ends of the winding, ie, where the anode of V2B and R27 connect to one end and the anode of V3B and R28 connect to the other end - you should be able to identify these from the circuit and what you have in front of you on the amplifier chassis.

The secondary will have a very low resistance of an ohm or so, which you have measured as just continuity.

[Techman]

Originally Posted by RoyceVM

1 and 4 had 189 ohms

You may have already measured the end to end readings without realising it and it's the one quoted above as 189 ohms. If it is, then this is probably correct and the transformer is fine, but just verify that this is definitely the case from my instructions in the previous post.

[RoyceVM]

Originally Posted by Techman

If you look at your circuit diagram that you posted you will see that there should be 5 connections to the primary. I think the readings that you've posted so far are ok, but the important one is to take a reading between the two ends of the winding, ie, where the anode of V2B and R27 connect to one end and the anode of V3B and R28 connect to the other end - you should be able to identify these from the circuit and what you have in front of you on the amplifier chassis.

The secondary will have a very low resistance of an ohm or so, which you have measured as just continuity.

Thank you! That is the lead I measured for pin 4 and pin 1 which was 189 ohms.
There is no center tap.

Pin 1 went to V3B and R28 and Pin 4 went to V2B and R27.

[Techman]

Originally Posted by RoyceVM

Thank you! That is the lead I measured for pin 4 and pin 1 which was 189 ohms.
There is no center tap.

Pin 1 went to V3B and R28 and Pin 4 went to V2B and R27.

Yes, you've got it - see my previous post #34.

[RoyceVM]

Now I have to change all that old paper capacitors. I need to identify it one by one, then order them and replace it with film capacitors.

[RoyceVM]

Got the ECC82 diagram

[Techman]

Well there's only the 4 that I showed you plus that Plessey electrolytic and it's job done!

There's others that you might want to replace, it's up to you, but you risk creating other faults as it's a bit of a rats nest in there. Replacing other components that don't really need replacing won't make the amplifier work any better and may even lead to the instability that these amplifiers are known for.

[RoyceVM]

Originally Posted by Techman

Yes, you've got it - see my previous post #34.

Thanks again for your help!