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Old 30th Aug 2017, 9:01 am   #1
Ekcoman
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Default PYE BLACK BOX 1004 transistor version, sound cut offs

Have a transistor Pye Black Box where the sounds cuts out and then returns. If you gently flick the stylus when sound is off then it returns. It's not the cartridge as tried three that have checked and are all working fine. Can find no issues with connections so has me baffled. Have taken it to an engineer friend who's a lot more proficient than me in such matters and he's struggling. Will return it to him to have another go. Can anyone help pointing him in the right direction as what might be the issue.
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Old 30th Aug 2017, 10:47 am   #2
Edward Huggins
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

This does sound just like a cartridge/connector issue. Have you used a contact cleaner?
If it was an amplifier failure, flickng the stylus would make no difference.
If it is an amplifier problem then one or more of the old Newmarket germanium transistors is breaking down. These amps are not the easiest to service.
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Old 30th Aug 2017, 10:54 am   #3
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

You have to determine when you say the sound cuts out, is there still sound from the speaker, there should be a quiet hum or hiss. As it is a transistor player it is safe to touch the back connections of the pickup cartridge without concern of it being a live chassis and with the volume control turned up this will produce a loud hum if the connections to the amplifier and the amplifier itself is working. It is then a fault in the cartridge, if there is no loud hum or intermittent hum then there is a fault somewhere in the wiring from the cartridge, possibly where it goes through the pivot point of the tone arm. Or a loose connection in the amplifier wiring.
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Old 30th Aug 2017, 11:39 am   #4
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

To try and clarify a bit the sound drops off in volume to a low level, it doesn't go silent. It can sometimes come back of its own accord. Was thinking of contact cleaner on the pots so might start there as not sure if done. It can happily play two sides of an LP but then can drop out on a first play. Easier to identify if consistently played up.
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Old 30th Aug 2017, 5:52 pm   #5
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Now suspect it was the metal connectors at the back of the cartridge after all. Damn sure I checked this but maybe mislead by the fact that the plastic sheath surrounding the connectors was leading me to believe there was good contact. Talk about missing the blatant obvious. Played 3 x lps sides and all perfect. I changed the BSR TC8 stereo cart for a Ronette 105 that think new/old stock. Sound improved too but not counting chickens just yet. Thanks Edward & Geoff for your replies.
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Old 30th Aug 2017, 8:16 pm   #6
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

That sounds more like it! The Ronette cartridge may weigh less than the BSR TC8S so just check. It should track at about 3.5/4 grams. Assume you have bridged the LH and RH channels on this for the Mono amplifier?
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Old 1st Sep 2017, 9:29 am   #7
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Looks as though the issue was with the volume/off-on pot as sound dropped out after making sure all connections to cart were sound. Did my best to get some switch cleaner in and the wriggled knob as well as turned it on countless times. Seems ok now as played 6 LP sides last night with no drop outs. Now holding breath.
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Old 3rd Sep 2017, 9:01 am   #8
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Back to square one with this as not a cartridge issue and don't suspect the pot. Dropping out sound to very low level as we were and only increasing volume slowly to a higher level kicks the sound back in but anti-social on neighbours when it blares out. Any other suggestions as where to go next?
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Old 3rd Sep 2017, 9:31 am   #9
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

I would look at how the DC voltages vary. A leaky transistor could heat up, then cool down.

Make a simple audio generator to input a signal at various points. I have made one using a 4093 to produce audio, RF and modulated RF.
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Old 3rd Sep 2017, 10:47 am   #10
Edward Huggins
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

The amplifier circuit on this can be rather fussy to fix. What experience does the OP have of early transistor equipment trouble shooting and repairing?
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Old 3rd Sep 2017, 11:19 am   #11
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Might just be as simple as a dry joint. Increasing the signal level makes it "bridge" the poor connection and it works for a while. This can also occur with a transistor.
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Old 3rd Sep 2017, 11:24 am   #12
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Does this player have a headphone socket? If it does it may be the culprit. Oxidised contacts frequently go open or high resistance and the shock of a burst of high volume can wake them up. Speaker connections likewise and I once had the speech-coil connections (the braid wires themselves that go from the tags to the coil) become intermittent.
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Old 3rd Sep 2017, 3:20 pm   #13
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

There is no Headphone socket or any other socket on these.
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Old 4th Sep 2017, 7:32 am   #14
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Thanks again for inputs guys. Contacting my engineer friend this morning to see if he is willing to investigate further or would rather pass on this occasion. Using my older BB at he moment with BSR UA8 deck.
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Old 4th Sep 2017, 9:45 am   #15
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Quote:
Originally Posted by vidjoman View Post
Might just be as simple as a dry joint. Increasing the signal level makes it "bridge" the poor connection and it works for a while. This can also occur with a transistor.
I've seen this behaviour numerous times on various equipment.

Try the obvious things like removing/re-seating plugs and push-on terminals etc. (with the power off), as well as a bit of careful poking around with an insulated prod (e.g. a chopstick) while it's on and driving the amp from a signal generator (or radio tuner, MP3 player or what have you).

A can of freezer spray might be of use identifying a faulty transistor.

Nick.

Last edited by Nickthedentist; 4th Sep 2017 at 9:51 am.
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Old 11th Oct 2017, 7:15 am   #16
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Default Re: PYE BLACK BOX 1004 transistor version, sound cut offs

Just to update it was a faulty transistor that was eventually tracked down. Rather a time consuming exercise being a very intermittent fault. Bless would accept any payment. Must admit the sound on this model of BB is exceptional and have to say might have the edge on the other earlier valve models of BB. I shouldn't be saying that should I? Moderator can now close this thread and thanks to all contributors to this thread.
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