Re: 7603 P.S. cans, slow warm-up and focus control


One thing to note on the 7603, if you remove the power supply Take LOTS of photos and triple check the connectors before turning the scope on. There are 2 connectors in particular that need attention. I am not in the lab at the moment so I can get the numbers later tonight. but looking from the back of the scope they are left side and up top on the top most board. The is the distribution point for the LV supply and also the test point for the LV voltages. DO NOT get the 2 back to back connectors reversed. The scope will be destroyed. What happens is the 130 V rail gets fed in to most of the IC's in the wrong place frying all of them. If I remember correctly the connectors are tan and black.


-----Original Message-----
From: <> On Behalf Of Jean-Paul
Sent: Wednesday, July 7, 2021 7:27 AM
Subject: Re: [TekScopes] 7603 P.S. cans, slow warm-up and focus control

Mark: My 7603 is like all other TEK scopes I have, normal warmup time.

Your symptoms sound like old caps in LV and HV PS, also check the Z axis circuit.

WHY did the focus pot burn: A big clew !

Suggest to get a HV probe or VOM DVM adapter, and go thru all voltages in the HV/CRT ckt.

The HV transformers are suspect on some old TEK scopes due to cracking or deteriorating insulation.

Bon Chance


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