3-pin capacitors - UK Vintage Radio Repair and Restoration Discussion Forum

Pinörkel · 6th Jun 2020, 8:50 pm

Hello,
I am in the process of restoring/replacing some capacitors in my vintage test equipment and need a little help. In my Telequipment D755 oscilloscope, there were once(before a previous owner replaced them with crap) some beautiful large blue snap-in filter capacitors with 3 pins made by Erie Electronics. They measured about 25 mm in diameter and were about 50 mm to 55 mm high. Although a set of original ones for restoration seems to be unobtainable, I now finally managed to find some 3-pin replacement capacitors with matching electrical values. Unfortunately, the replacements are only 40 mm high(see image) and have a different pin configuration.

On the original capacitors, there was one pin soldered to an unconnected pad on the PCB for stability reasons. On the new ones, the positive pin and the stability pin are swapped. This means that putting them into the PCB the same way as the original ones will not work. Does anyone know, if I can safely just connect the positive pin and the stability pin with a wire, without any bad side effects? The resistance between the stability pin and the positive and negative pins is in the order of one to ten mega ohms. So the stability pin does not seem to be connected to anything. Is there a standard pinout for these 3-pin capacitors?

Radio Wrangler · 6th Jun 2020, 9:08 pm

If your ohmmeter shows such a large value, it looks like the stability pin is not connected, so you should be OK just adding a bridge wire.

Some three terminal capacitors duplicated the -ve terminal and had additional connection tapes from the negative foil in the swiss-roll. this helped with stray R and stray L so they were intended for high frequency SMPS use, but the label indicated the dual -ve terminals.

The stablilty pin helps during wave-soldering in manufacture, but it also improves reliability if subject to vibration... two-pinned capacitor can flex their pins in a sort of hinge mode until the metal fatigues and cracks.

David

Pinörkel · 6th Jun 2020, 9:45 pm

Thank you for the fast reply. In this case, I will put together a small rectifier circuit for testing this outside the oscilloscope first. Seems I was kind of lucky to still find some 2200 μF, 63 V caps with three pins. I have another missing cap with 330 μF and 200 V that I cannot find anywhere with a 3-pin layout. Seems nearly all snap-in caps are 2-pin nowadays and get fixed with some additional silicone based glue. I would like to have a set of original caps, where I could hide a new capacitor inside the old shell. But those are really hard to source. Instead, I will try and find some similar sized 3-pin capacitors and try to recreate the original blue transparent heat shrink tubing with yellow print.

Denis

Electronpusher0 · 6th Jun 2020, 10:16 pm

I have the attached capacitors you can have if you want them. They are the same size as you want, 50mm high (body) height above board 57mm, dia 25mm.
They came from some scope spares that Ed Dinning let me have,
They are the same type of 3 pin as you describe about 8mm between the red pins and the unmarked pin is about 12mm away from the plane of the other 2.
They are not the right value unfortunately being 470uF 100V but if you are going to re-stuff them they may do for you.
If you want them they are yours for the cost of postage.

Peter

Edit, the pins may be marked one red and one yellow, hard to tell.

Pinörkel · 7th Jun 2020, 2:35 pm

Hello Peter, thank you for the kind offer. Those seem to have the exact size I would need. May I contact you via PM when I have acquired the remaining restoration ingredients and figured out a minimum damage strategy to open these caps? I still need to find some heat shrink tube with perfectly matching color and diameter.

The red and yellow markings on the pin are characteristic for these ones. Yellow usually denotes the dummy pin, red the positive pin, and the negative pin is unmarked. Erie even used to write this pin assignment on the heat shrink tube on larger capacitors. I have attached a picture of the three needed caps like in my D75. The red one is a PYE 330 μF.

Denis

Electronpusher0 · 7th Jun 2020, 3:10 pm

Quote:

Originally Posted by Pinörkel

Hello Peter, thank you for the kind offer. Those seem to have the exact size I would need. May I contact you via PM when I have acquired the remaining restoration ingredients and figured out a minimum damage strategy to open these caps?

Denis

Yes of course.
Peter

6th Jun 2020, 8:50 pm	#1
Pinörkel Pentode Join Date: Jun 2019 Location: Dortmund, Germany Posts: 161	3-pin capacitors Hello, I am in the process of restoring/replacing some capacitors in my vintage test equipment and need a little help. In my Telequipment D755 oscilloscope, there were once(before a previous owner replaced them with crap) some beautiful large blue snap-in filter capacitors with 3 pins made by Erie Electronics. They measured about 25 mm in diameter and were about 50 mm to 55 mm high. Although a set of original ones for restoration seems to be unobtainable, I now finally managed to find some 3-pin replacement capacitors with matching electrical values. Unfortunately, the replacements are only 40 mm high(see image) and have a different pin configuration. On the original capacitors, there was one pin soldered to an unconnected pad on the PCB for stability reasons. On the new ones, the positive pin and the stability pin are swapped. This means that putting them into the PCB the same way as the original ones will not work. Does anyone know, if I can safely just connect the positive pin and the stability pin with a wire, without any bad side effects? The resistance between the stability pin and the positive and negative pins is in the order of one to ten mega ohms. So the stability pin does not seem to be connected to anything. Is there a standard pinout for these 3-pin capacitors? Attached Thumbnails

6th Jun 2020, 9:08 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: 3-pin capacitors If your ohmmeter shows such a large value, it looks like the stability pin is not connected, so you should be OK just adding a bridge wire. Some three terminal capacitors duplicated the -ve terminal and had additional connection tapes from the negative foil in the swiss-roll. this helped with stray R and stray L so they were intended for high frequency SMPS use, but the label indicated the dual -ve terminals. The stablilty pin helps during wave-soldering in manufacture, but it also improves reliability if subject to vibration... two-pinned capacitor can flex their pins in a sort of hinge mode until the metal fatigues and cracks. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

6th Jun 2020, 9:45 pm	#3
Pinörkel Pentode Join Date: Jun 2019 Location: Dortmund, Germany Posts: 161	Re: 3-pin capacitors Thank you for the fast reply. In this case, I will put together a small rectifier circuit for testing this outside the oscilloscope first. Seems I was kind of lucky to still find some 2200 μF, 63 V caps with three pins. I have another missing cap with 330 μF and 200 V that I cannot find anywhere with a 3-pin layout. Seems nearly all snap-in caps are 2-pin nowadays and get fixed with some additional silicone based glue. I would like to have a set of original caps, where I could hide a new capacitor inside the old shell. But those are really hard to source. Instead, I will try and find some similar sized 3-pin capacitors and try to recreate the original blue transparent heat shrink tubing with yellow print. Denis

6th Jun 2020, 10:16 pm	#4
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,294	Re: 3-pin capacitors I have the attached capacitors you can have if you want them. They are the same size as you want, 50mm high (body) height above board 57mm, dia 25mm. They came from some scope spares that Ed Dinning let me have, They are the same type of 3 pin as you describe about 8mm between the red pins and the unmarked pin is about 12mm away from the plane of the other 2. They are not the right value unfortunately being 470uF 100V but if you are going to re-stuff them they may do for you. If you want them they are yours for the cost of postage. Peter Edit, the pins may be marked one red and one yellow, hard to tell. Attached Thumbnails

7th Jun 2020, 2:35 pm	#5
Pinörkel Pentode Join Date: Jun 2019 Location: Dortmund, Germany Posts: 161	Re: 3-pin capacitors Hello Peter, thank you for the kind offer. Those seem to have the exact size I would need. May I contact you via PM when I have acquired the remaining restoration ingredients and figured out a minimum damage strategy to open these caps? I still need to find some heat shrink tube with perfectly matching color and diameter. The red and yellow markings on the pin are characteristic for these ones. Yellow usually denotes the dummy pin, red the positive pin, and the negative pin is unmarked. Erie even used to write this pin assignment on the heat shrink tube on larger capacitors. I have attached a picture of the three needed caps like in my D75. The red one is a PYE 330 μF. Denis Attached Thumbnails