I have a Tektronix Type 130 on the bench and I need some help IDing some parts - Page 1
Forum section: electronics / repair

author: Zenwizard
author_rank: Regular Contributor
timestamp: January 13, 2024, 05:21:04 pm
content: Attached a is picture of the parts in question. Does anyone know the construction of the capacitors pictured? The service manual is not clear as to the construction early units used paper caps later units all ceramic but the server manual does not note serial number change over. My main question is do they need to be swapped out as part of my restoration process or are they good to leave in place The caps in question are the ERIE components.Zen

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: January 13, 2024, 06:03:31 pm
content: From what I can find from the service manual, "PT" capacitors.Possibly Polytetrafluoroethylene Film Capacitors?I think you can just replace then with ceramics or modern film caps.I do not think those capacitors need replacing though. They're ceramic or film, and those tend to be pretty reliable. I don't see paper capacitors in the parts list.They also do not look like paper. too shiny in my opinion

author: BlownUpCapacitor
author_rank: Frequent Contributor
timestamp: January 13, 2024, 06:04:53 pm
content: Screenshot here

author: jpanhalt
author_rank: Super Contributor
timestamp: January 13, 2024, 06:16:42 pm
content: PT may also mean polyethylene terephthalate (now known as polyester (PET)). Probably high quality and not only don't need to be replaced but probably shouldn't be replaced.

author: TimFox
author_rank: Super Contributor
timestamp: January 13, 2024, 06:19:43 pm
content: The large axial lead capacitors with an “outer foil” band are paper in my 130.Upon advice, I replaced them all with modern polypropylene units: the removed units measured very low Q, and I suspect water infiltration.After replacing those 10% tolerance parts, you will need to recalibrate.I doubt strongly that PTFE parts were used in this meter.

author: Zenwizard
author_rank: Regular Contributor
timestamp: January 13, 2024, 06:23:15 pm
content: I did check the leakage on my SMU 2450 in the lab up to 100 Vdc leakage was .035 nA or 35pA. I also checked them for DC leakage on a IT28 and they passed with flying colors up to 350Vdc my line voltage runs a but hot so the 400 Vdc test on the IT-28 hit more like 435 over stress them.Zen

author: TimFox
author_rank: Super Contributor
timestamp: January 13, 2024, 08:47:11 pm
content: My 130 is probably older than yours.The front panel calls it an “L, C” meter.Does yours say “L - C” meter instead?

author: Zenwizard
author_rank: Regular Contributor
timestamp: January 13, 2024, 11:07:23 pm
content: Mine does say L-C meter. It sounds like you have the older style chassis.Zen

author: David Hess
author_rank: Super Contributor
timestamp: January 13, 2024, 11:35:28 pm
content: The only references I found say that the maroon axial ERIE capacitors are metal film, so they should be good. I thought they were paper like the Motorola ones which look very similar.I checked the Tektronix capacitor book and the part numbers are too old to be listed.

author: TimFox
author_rank: Super Contributor
timestamp: January 13, 2024, 11:44:44 pm
content: Presumably, that’s metallized film.At that era, that is probably polyester/Mylar/polyethylene terphtalate.

author: Dave Wise
author_rank: Regular Contributor
timestamp: January 15, 2024, 09:20:29 pm
content: Those particular caps are used in the charge pump. Tek printed the meter scale to fit a brand-new instrument whose caps had dielectric absorption normal for that type. At the time the 130 was designed, that was probably paper/oil Sprague "Telecap" Black Beauty, commonly referred to as Bumblebee today. When new, those paper caps had more DA than polyester, and they've increased over time in both value and DA. With my own 130 (which came with Sprague 160P "DiFilm" paper/plastic with "HCX" impregnant) I noticed a high reading at mid-scale when top and bottom were trimmed. When I replaced them with polypropylene, I got a low mid-scale reading. I believe plastic istoo good. I ended up faking some DA by paralleling each cap with a series RC. I got good results when I set the added time constant to match the mid-scale pulse frequency, while setting R to give the right amount of correction. I did this exercise with an RC substitution box then tacked in the results. It might be gilding the lily but I had fun.