Hello All, I have been after a Philips PM 5326 r.f. generator for a few years now. One aimed at radio and television receivers. I have the older PM 5334 which I have had for about 25 years and works well.
I have had a quick run through it and found only one range was working but solved by operating the frequency range switches and all but two ranges are now working. The sweeper works o.k. The 1khz audio oscillator is dead. The r.f. tuning control does nothing, think the grease has gone a bit stiff? The frequency counter was bang on 10Mhz after the 30 minuet warm up period when checked against GPS.
So there are a few problems to work through. I did one about 15 years ago for a college and that went well.
This is my other older unit which was ex Rediffusion. It had a few scan linearity problems which was caused by series diodes, a couple having gone s/c.
Got a bit of fun ahead of me when time permits.
Hi Adrian,
yes, the grease does seize on the tuning system - one of mine did that. I also have one where some of the ranges don't work.
You may find this article of interest: https://www.vk5tm.com/gallery/pm5326/pm5326.php
I'm minded to investigate that myself. The beauty of that conversion is that there are no alterations to the front panel.
@cathovisor I'm have read about that conversion too. Very interesting. Time to start collecting a few bits. Don't think there is a PCB available?
No, the DDS module seems to be a commercially available one whilst the PIC interface is simply built on Veroboard before being placed in a small diecast box.
I've sent you a link to what appears to be the DDS module on eBay.
Going through the instrument, 3 r.f. ranges don't work. Audio oscillator not running and of course the tuning capacitor completely seized.
Tackle the tuning capacitor first. I couldn't move this at all. Had to apply Plus Gas which eventually allowed me to move it and after a struggle withdraw the shaft from and capacitor body. A lot of effort to remove the old grease at it was more like set varnish, never seen one as pad as this before.. The vain cog has two parts as it is anti-backlash so has two cogs and a tension spring. Of course the spring fell off. All cleaned and now re-greased and working fine.
Can now tune across the range.
Next was to look at the audio 1kHz generator which uses a CA3086 transistor array IC. Checked the application of 12V when the audio modulation is selected which was correct. In this chip has 5 transistors within but all the transistor legs are available on the IC pins. Ran trough these and all transistors appeared to be in order. Next checked a couple of 1uF capacitors which are part of the audio oscillator and these where indeed open circuit. Replaced these and a 2.2uF capacitor and the audio oscillator is now up and running again so I now have 1kHz am and fm modulation working again.
Next to tackle the 3 r.f. ranges that don't work. Looking at the carrier generator board, each range is selected by a reed relay driven by off a BCD to Decimal decoder IC 7445. This is indeed doing its job but 3 of the reeds are not operating. The coils are driven from 5 volts. I have ordered some reeds but a bit out of my depth here as I don't know how the sensitivity of a reed is stated. When these arrive I will see how we get on but the fitted reeds are small, just over 10mm long and 2mm or less in diameter. Picture below
Next to tackle the 3 r.f. ranges that don't work. Looking at the carrier generator board, each range is selected by a reed relay driven by off a BCD to Decimal decoder IC 7445. This is indeed doing its job but 3 of the reeds are not operating. The coils are driven from 5 volts. I have ordered some reeds but a bit out of my depth here as I don't know how the sensitivity of a reed is stated. When these arrive I will see how we get on but the fitted reeds are small, just over 10mm long and 2mm or less in diameter. Picture below
This is the exact issue I have with one of my examples. I have to say I find these generators particularly user-hostile compared to their predecessor, the PM5324 "Blue Cube".
I shall follow this with interest.
Postman has just called and brought me some reed switches. I ordered 4 different types. 3 of them are half the size of the original reeds. One was exactly the same. There is not a lot of room either side of the coils. I unsoldered each end of the reed then snip or break one end and pull out the reed towards the diecast box side of the coil. Insert the new reed from the diecast box wall and pull trough. Bend and re-solder to the coil mounting tags. Its tight so be careful and don't have the reed wire pulling on the reed ends, they can crack over time. All is now working correctly, all ranges now working. Study the picture from my last comment. No missed latching operates faultlessly. Now to work through the rest of the instrument. Reed switches came from Farnell. My test method is measure which coil is being operated, will have 4.9V across it and with the voltmeter still on volts measure across the reed switch, should be 0 volts. If it is showing 0.8 volts the reed is duff. Part numbers shown in attached.
Hurty
@cathovisor The PM5324 you mention, I never realised it had the sweep function! I see it does but does not seem to cover the TV i.f. range? As I mentioned at the beginning I have the PM5334 which sweeps everything domestic including the TV UHF band.
@hurty I think that was why you had the separate PM5324 for radio and the PM5334 for TV - they both have a roughly similar family resemblance. The PM5326 is from a newer generation of test instruments though.
As luck would have it, I was making an order to CPC and right at the last moment prior to clicking "pay now" I thought I'd see if they had those reed switches you bought - and they do, so I ordered some. Thanks for the tip 👍
@cathovisor Was that the switches for the Marconi 2022 or the reeds for the PM5326?. The Philips is fully working now but
I have yet to change the switch tops on the 2022.
@hurty The reeds for the PM5326. At some point I need to investigate making replacement springs for the push-buttons in my HP 8903 audio analyser.
