33/303 noisy on switch off

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19-Feb-2018 04:38 PM

QuadOAP

QuadOAP

Posts: 12

I completed the the refurbishment of both a 33 and 303 recently. The system is now very noisy when I switch it off. I get like a loud discharge through the speakers and it continues on for a number of seconds. 

I have only recently received this system, which has been in storage for many years, so I don't know its history.

Any suggestions as to where the problem lies?

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20-Feb-2018 12:02 AM

EJP

EJP

Posts: 1484

1. Isolate whether it's the 33 or the 303, by disconnecting the 4-pin signal interconnect and repeating the experiment.

2. If it's the 303, change Tr100 in both channels.

3. If it's the 33, remove the Tape Adapter board and see if it still happens. If it doesn't, change the transistors on that board. If it does, change the transistors on the two amplifier boards.
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13-Mar-2018 03:58 PM

QuadOAP

QuadOAP

Posts: 12

Thanks for your advice.

On farther investigation the fault lay in the 33 not the 303. It cleared when I replaced the BC109s on the amplifier boards. The 33 was also noisy when using the cancel button  The switch required a number of cleans before the crackling disappeared. This may have been two separate faults as the 33 had been in storage for a quite some time.

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