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Old 29th Jul 2019, 6:21 pm   #46
Pinörkel
Pentode
 
Join Date: Jun 2019
Location: Dortmund, Germany
Posts: 161
Default Re: Telequipment D75 scope.

Quote:
Originally Posted by Alistair D View Post
The voltages I measured were across D604 as you said. When I am next working on the scope I will do one set ground referenced.

No need to mark up a diagram, a list of component references will be fine.
I did some additional measurements to further pin down the location of the fault, but did not succeed. From the fact that channel 1 works comparatively well, I conclude that the voltage drift at D604 can only be a small part of the problem. A second thorough cleaning of the corresponding vertical position double potentiometer did not solve the problem. At least It killed some of the pots wiggle sensitivity. Maybe I will get an optical interface adapter for my DMM to log the voltage drifts on my PC.

Quote:
Originally Posted by MrBungle View Post
Just a heads up here and I hope this doesn't violate the ebay policy on here but there's a load of telequipment plugins appeared on ebay here: https://www.ebay.co.uk/itm/362703426707
Thank you very much for the hint. I'll keep an eye on that. Some of these seem to have a fair bit of cosmetic damage and all serial number plates have been removed. So maybe they could be good for spare parts. They seem to only ship to UK though.

Apart from that, I could not stop myself from acquiring a D755 Opt 66 with a V4 and an S2C amplifier which will arrive this week (X-Y mode. Yay!). Unfortunately the units case was painted deep blue by the former owners and modified with a custom power cord (drilled a hole in the case for that). That makes it unsuitable for a restauration. The modules seem to be sort of OK, but the mainframe has some serious corrosion issues due to moisture. As I could see on some supplied images, nearly all the trim pots on PC147 and the PCBs around the tube have to be replaced. Hopefully the unit does not get damaged during transport. IMHO the most interesting aspect of this unit is, that the modules use much newer electric and mechanical parts than the ones on my D75. The push switches and black plastic button rods resemble those, I once saw in a Tek 465b. Most electronic components like resistors are much newer models than in my D75. However I will first concentrate to fix my D75. Maybe the modules from the D755 can help with that.
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