Pattern generator (Arlunya PG100E) issue / question - Page 1
Forum section: electronics / repair

author: 002
author_rank: Newbie
timestamp: April 14, 2021, 05:56:26 am
content: Hi,I recently obtained an old Arlunya pattern generator on eBay so I can use it on my CRTs. I am very happy to own it and was excited to test it out, which I did - and all the functions I've tested so far appear to be working, however there was a little bit of an issue...After I was messing around with it for 5 minutes or so, I heard a fizzle and the unit started filling with smoke. I quickly switched it off, although I did note that it was still displaying patterns just fine before switching it off.I took the lid off and did a visual inspection where I noticed that it looks like some winding component burnt up. I was wondering if someone may be able to help me identify it so I can (hopefully) get a suitable replacement. I've attached some pictures of it - I assume it is some sort of inductor? One picture shows it in place next to one that looks much healthier, and the other picture is the crispy boy removed.Thank you in advance for any help.

author: TheMG
author_rank: Frequent Contributor
timestamp: April 14, 2021, 02:16:29 pm
content: Choke inductor. Measure the good one (out of circuit) with an LCR meter to obtain inductance value. Exact value of replacement is probably not critical, as it's likely used for some kind of power supply filtering/decoupling. However, the replacement must have a sufficient current rating. This can be estimate by measuring the resistance, and calculating the maximum current within reasonable power dissipation.Before replacing it though, you'll have to do some more troubleshooting. For it to burn up like that means excessive current has flowed through it. You will have to figure out why, or the new choke will likely burn up right away. Could be as simple as a failed capacitor somewhere.

author: 002
author_rank: Newbie
timestamp: April 15, 2021, 12:52:04 am
content: Hi TheMG - thanks very much for the reply. I've ordered an LCR meter on eBay and will test the choke when it arrives.You'll have to forgive me as I am somewhat new to this hobby, but how would I calculate the current rating with the resistance and inductance values of the choke inductor?I had a look at some of the ceramic capacitors that are directly nearby the choke - I think they are too small for my meter to measure at 39pF. Do you think it could be these little capacitors? I measured the ESR values of all of the electrolytic capacitors and they all seem healthy in that respect (there's only maybe a dozen or so in the entire unit).I've attached some more pictures too if anything stands out to people much wiser than I am.

author: 002
author_rank: Newbie
timestamp: May 03, 2021, 03:44:18 am
content: OK figured I would post a little update. It looks like the choke inductor was a red herring and tests fine with the DE5000, matching the one beside it at 4Ω and ~100µH.I looked everywhere on all the boards for something burnt out before noticing something tucked down on the transformer. It is some sort of weird looking old capacitor that blew open.I'll replace it and test again I suppose.Edit: Reading up more about it, I believe this is a Y2-class safety capacitor designed to filter out high frequency noise. It probably explains why many of the patterns had shimmering / wobbliness but the unit is otherwise working fine. The spot and circle generator don't work at all but I guess that's another problem entirely :<