TEK 465 with DM44 o display

[Andymarkt]

Hello to all.
I am a new member of the forum although I have been lurking for some time trying to learn in the background but now have to ask for help with my defective TEK 465 oscilloscope.

The primary symptoms was - no display. After checking here and looking at a downloaded service manual I found that the -8v read at TP1568 was actually +0.8v (read using my very old but functional Fluke 8050A meter). Further checks on the surrounding test points showed:
+110v read at TP1518 showed 110.2v, +55v read at TP1536 read 55v, +15v read at TP1548 read 15v, +5v read at TP1558 showed 4.4v.

Being a bit optimistic I thought that as the scope had been in storage for a couple of years in the loft that the PSU electrolytic's had failed so I replaced them using a guide I found written by Ron Childress. This did mean that now the indicator lights on the Volts/division controls are now illuminated and if I twist the VAR buttons in the volts/dive and time/division buttons the un-calibrated indicators light up.

Whilst the caps were out I checked the resistance of the rectifiers in the area of the caps and all appeared to be OK - no shorts or opens on any of the packages that I measured.

Now also on applying power to the scope there is a flash of display in the crt at the bottom of the screen only momentary in the shape of an inverted wedge and the crackle as HT seems to come up. In the high voltage area of the main pcb  there are a couple of what appear to be neon's which are lit up when the scope is powered up and down.

Further checking on Q1566 which is I hope the regulator for the -8v rails is Base - 0.8v, Collector - 0.1v and emitter - 0.1v.

The beam finder and intensity controls appear to have no affect even when used together.

I have been trying to work from a downloaded service manual but it appears to be incomplete. I have ordered a hopefully superior one from Artek manuals but have not yet received e-mail notification of the download location.

Apologies if I have rambled on but I thought I had better give all the information I have available, as this is my first post please accept my apologies for any breach of etiquette.

Thanks for your patience and any guidance offered would be appreciated.

[Andymarkt]

Update. After rechecking the rectifiers towards the rear of the pcb, CR1561 was replaced and now the -8 voltage on TP1568 shows as 7.99v and the 5v supply at TP1558 is 5v. There is now a display that can be moved using the horizontal and vertical controls but the display is only 7.5cm long on a 10cm crt screen. The focus control is now functional and intensity seems to be OK as well although the pot seems stiff.

Now to start on the trace length issue.....

[echen1024]

Update. After rechecking the rectifiers towards the rear of the pcb, CR1561 was replaced and now the -8 voltage on TP1568 shows as 7.99v and the 5v supply at TP1558 is 5v. There is now a display that can be moved using the horizontal and vertical controls but the display is only 7.5cm long on a 10cm crt screen. The focus control is now functional and intensity seems to be OK as well although the pot seems stiff.

Now to start on the trace length issue.....

That's probably just a cal issue. Look in the service manual for all the pot positions, and find the one that matches your problem. Here:

[bigpimp347]

old post i know but....


i have said units, 465 and DM-44

465 seems to work ok..
DM-44 is just sat on 0

any ideas as to why the VM doesn't read ??

i see there is a simple glass bulb fuse which seems ok to look at,
but any ideas ?

i get voltage to the switches on the front to change values, but nothing on the display..which was the main reason i wanted it..

sorry it's late