Quote:
Originally Posted by Boater Sam
The different speakers. Both channels?
Are we talking transistors here? If so the output stage is oscillating possibly due to duff caps and your speakers in the shop load or unload it enough to prevent it.
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Both channels are affected in exactly the same way, it is a transistorised amplifier, can try different speakers later.
Quote:
Originally Posted by dragonser
Hi,
just a couple of random thoughts !
Is the earth ( ground ) connection good at the customer's house ?
are the speakers nearby to the radiogram ?
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No idea about the earth connection, but removing the earth has no effect. The speakers are built into the cabinet so very close by.
Quote:
Originally Posted by RojDW48
You have probably investigated this - but back in the 70s I had a similar problem with a Rogers Ravensbourne amp - intermittent motorboating on the MM disc input. It turned out to be a cracked resistor in the phono stage. There were 4 sensitivity settings selectable by prodding combinations of 2 buttons. Prodding enthusiastically, of course, resulted in the problem disappearing temporarily!
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Unlikely, I did a lot of prodding both in the customers home and the workshop.
Quote:
Originally Posted by JohnBHanson
Stepping back a bit could this be acoustic coupling between the speakers and the gram pickup? This would account for it being site dependent.
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Absolutely not, the noise is still there whether playing a record or not or when the cartridge is removed from the deck. Its also there when the inputs are grounded.