UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Closed Thread
 
Thread Tools
Old 14th May 2018, 5:22 pm   #1
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
Default Philips PM 3365A - wobbly display

The PM 3365A is one of my favourite 'scopes, it has everything you need and nothing you don't. I've designed more stuff using these than any other model, they are so easy to operate.

However, a common problem seems to be a "ragged" display when switched on from cold, the last 2 or 3 I've seen have all done it. It shows up worse in digital than in analogue mode, where the text at the bottom is unstable (especially at the edges) and the traces noisier than they should be. After half an hour or so the situation improves greatly and everything functions normally. In analogue mode the symptoms are less severe, but still noticeable for critical work.

At a guess it looks like hash from the power supply or the EHT generator getting into the rest of the circuit, however a quick check around reveals nothing obvious amiss. The layout and construction of the interior does not lend itself to easy fault finding, does anyone have any experience of fixing these?
Studio263 is offline  
Old 14th May 2018, 5:37 pm   #2
chriswood1900
Octode
 
Join Date: Jan 2007
Location: Dorridge, West Midlands, UK.
Posts: 1,474
Default Re: Philips PM 3365A - wobbly display

In one I had all the small blue caps on the PSU were shot replacing them brought it back to proper working order, I believe it is a common problem on these scopes.
Fish out your ESR meter.
see also here https://www.youtube.com/watch?v=evGf4LMaixI
Chris
chriswood1900 is online now  
Old 16th May 2018, 9:29 am   #3
Studio263
Octode
 
Studio263's Avatar
 
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
Default Re: Philips PM 3365A - wobbly display

Thanks for the tip - they all look OK and nothing gets hot in that area but appearances can be deceiving. Its a shame that the double sided print makes it so difficult to remove and test things but hopefully it will be working properly again soon.
Studio263 is offline  
Old 16th May 2018, 11:37 am   #4
MrBungle
Dekatron
 
MrBungle's Avatar
 
Join Date: Jun 2016
Location: London, UK.
Posts: 3,687
Default Re: Philips PM 3365A - wobbly display

Agree with chriswood1900. I had a PM3315 from Pamphonica a year or so ago now. That had a shorted Philips blue axial capacitor in it. Eventually they go high ESR which drags the rails down and then the power supply starts dropping out.

Also make sure you replace any of the RIFA gold ones in the inlet section. They are at prime exploding age at the moment and make a right mess!
MrBungle is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 4:22 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.