Teardown and Repair of an Philips PM 5771 100Mhz Pulse Generator - Page 1
Forum section: electronics / testgear

author: Alfons
author_rank: Regular Contributor
timestamp: September 28, 2019, 12:52:45 pm
content: Here's my new old Philips PM 5771 Pulse Generator. Fresh from Ebay.I was lucky because the device is fundamentally functional. Unfortunately, the signals do not always look good, which is due to the switches and potentiometers that need to be cleaned. In addition, the Elkos seem pretty drained, even if the power supply still works. Capacity and ESR is OK, but Vloss is very high.The optical condition is OK, no damage. Inside, the device looks untouched and full of dust.Here are some pictures of the structure. As usual at the time of manufacture, the frame is made of solid cast aluminum profiles so you can repair the unit very well. Everything is already arranged accessible.After a short test run, I find that it is even below the 2.5ns rise time something, I could measure 2ns at about 110 MHz. Above all, problems make the pot for the delay setting. Producing a clean signal when the delay is on is dire. It works, but not clean in all positions.I will restore the device gradually. Need some advice about cleaning the pots. These are fully enclosed and high quality.

author: Alfons
author_rank: Regular Contributor
timestamp: September 28, 2019, 04:03:58 pm
content: And more games: Does not replace a high-quality Time Mark generator, but it's enough to calibrate my old 475 and 7603. But first you have to understand how to set the device. Each position of a button affects the position of another.

author: med6753
author_rank: Super Contributor
timestamp: September 28, 2019, 07:10:06 pm
content: Why no cabinet on the 2467? While the risk is minimal the best optimum cooling of U800 is with the cabinet in place which generates airflow across it's surface. Out in the open as yours appears to be disrupts that airflow....unless you have a fan down there that I can't see.

author: Alfons
author_rank: Regular Contributor
timestamp: September 28, 2019, 07:45:04 pm
content: Thanks for the attention. Of course there is a big fan under the device. That's why he also stands on wooden blocks, so there is room for it. I know that it has to be cooled. I have to do a little bit on the device, so it's open.

author: tautech
author_rank: Super Contributor
timestamp: September 28, 2019, 08:06:37 pm
content: Congrats.Only the 2nd one I've seen other than one a buddy has had for years.Indeed, quite useful for doing Cal on sub 100 MHz CRO's.Service manuals were available online and if I get time I'll come back with a link to one.

author: Alfons
author_rank: Regular Contributor
timestamp: September 28, 2019, 08:15:13 pm
content: Thanks, I already found the service manual.It says, that you should take silver solder for soldering. Is the usual silver solder enough?

author: tautech
author_rank: Super Contributor
timestamp: September 28, 2019, 08:39:12 pm
content: Quote from: Alfons on September 28, 2019, 08:15:13 pmIMO yes.Something that should be in any serious restorers solder collection is some 2% silver solder.

author: tautech
author_rank: Super Contributor
timestamp: September 28, 2019, 09:42:06 pm
content: Quote from: Alfons on September 28, 2019, 08:15:13 pmAdding a link for others:https://elektrotanya.com/philips_pm5771_100mhz_pulse_generator_1973_sm.pdf/download.html3.6 MB

author: Alfons
author_rank: Regular Contributor
timestamp: October 04, 2019, 07:41:51 pm
content: I did a little bit. I cleaned the case and the switches. I did not touch the pots because I have no experience and it was too time-consuming. Maybe later. I exchanged all Ekos in the power supply and the control board. Except for adjusting the symmetry of the sync-out and thus the frequency, I have nothing set.Now the cutoff frequency fell by 2Mhz to about 102 Mhz, before I had 104 Mhz. But the signals look a bit better, less overshoots.Here are some pictures:It can be seen that the device reaches a Rise time of less than 2 ns at 100Mhz, at 10Mhz it is still 2ns. Also, the output signal at 50 MHz looks a bit cleaner now. It's amazing what such an old device does.

author: Alfons
author_rank: Regular Contributor
timestamp: October 04, 2019, 07:44:23 pm
content: And more...

author: tautech
author_rank: Super Contributor
timestamp: October 04, 2019, 08:10:40 pm
content: Yes they're a nice pulse gen and must have cost a bomb in their day as you see so few of them around. Even today you have to spend some good coin to get equipment that has similar specs.Good call on the pots, yes just give them some exercise/work.