Help Replacing Multi-Segment Capacitor - Page 1
Forum section: electronics / repair

author: Scottman
author_rank: Newbie
timestamp: October 23, 2020, 01:28:14 am
content: I am trying to bring to life a Hewlett-Packard Model 621 radio from the 1950s.There is a multi-segment electrolytic capacitor that I want to replace but I can't find a replacement for it. The segments are 30 Mfd, 20 Mfd, 20 Mfd, and 20 Mfd at 150v, 150v, 150v, 25v.Does anyone know of a place to find this capacitor? I can't find anything online and was wondering if I'm missing a source. Finally, if I can't find the right single unit can I just replace it with four single units of the appropriate strength? I'm knew to this so any thoughts are greatly appreciated.

author: valley001
author_rank: Frequent Contributor
timestamp: October 23, 2020, 01:55:11 am
content: I believe the common practice is to replace each with a separate capacitor of appropriate value. Some will "restuff" the old can with the new capacitors to retain the vintage look of things. I usually just install the separate caps when restoring old radios.

author: bdunham7
author_rank: Super Contributor
timestamp: October 23, 2020, 02:11:58 am
content: You'll never find an exact replacement. You can just use 4 separate units, and they don't have to match perfectly. If the original cap is metal cased and at least 1" diameter and 3" long, you can remove the guts and put 5 of something like these in:https://www.mouser.com/ProductDetail/Vishay/30D206G160DF2A?qs=PoiC2s2TC5hV4E9BHOqQsQ%3D%3DUse 2 in parallel for the 30 section and don't worry about the fact that the one original section had lower voltage. Restuffing like this can actually make things both neater and easier in the long run.

author: rvalente
author_rank: Frequent Contributor
timestamp: October 23, 2020, 02:21:50 am
content: Quote from: Scottman on October 23, 2020, 01:28:14 amCould you please post a pic of this radio? Never heard about it

author: bob91343
author_rank: Super Contributor
timestamp: October 23, 2020, 03:30:26 am
content: I don't think HP ever made radios. Perhaps it's Packard Bell. Or a car radio in a Packard vehicle. Or perhaps it's not a radio at all, but some kind of signal generator.

author: james_s
author_rank: Super Contributor
timestamp: October 23, 2020, 03:32:32 am
content: I usually re-stuff the original capacitor, modern parts are so much smaller that most of the time they will easily fit in the original space. If I'm feeling lazy I will just install the new capacitors under the chassis and leave the original in place but disconnected.

author: The Doktor
author_rank: Regular Contributor
timestamp: October 23, 2020, 05:12:50 am
content: I've not ordered from these folks yet, but I've seen people who claim good results. Custom multi section capacitors (including old style metal can).https://hayseedhamfest.com/Ed

author: Ian.M
author_rank: Super Contributor
timestamp: October 23, 2020, 07:14:36 am
content: 'Back in the day' electrolytic capacitors typically had very coarse tolerances for their value. e.g +100%, -50% wasn't exceptional. Therefore if you cant easily buy an exact match to the value, substitute the next higher preferred value in a 20% tolerance capacitor range, and it will almost certainly be within the original specifications. Similarly if the exact voltage rating isn't available, go for the next higher one. Therefore to replace the O.P.s capacitor, one is looking for one 33uF >150V cap, two 22uf >150V caps and one 22uF 25V or 35V cap.If you are going to re-stuff the can, its preferable to get 105 deg C rated ones, in case the ripple current causes them to run warmer than you expect, as they wont have any airflow in the can.

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 23, 2020, 09:06:38 pm
content: For what it's worth, found this listinghttps://www.ebay.com/itm/SAMS-PHOTOFACT-FOLDER-181-8-PACKARD-BELL-MODEL-621/254671204677?hash=item3b4b963145:g:iKcAAOSwjXRXZpKo

author: andy3055
author_rank: Super Contributor
timestamp: October 23, 2020, 09:30:34 pm
content: Diagram:https://www.tubesandmore.com/sites/default/files/schematics/packard_bell_co_621_pg23-4.png

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 23, 2020, 10:23:38 pm
content: Wow!No transformer, tube filaments in series, AC line half-wave rectified to make plate voltages +120, +110 and +85 volts.Probably no polarized plug but Bakelite case/knobs isolated.OK for the user but the service tech needs to observe plug polarity when the chassis is accessible, back off, knobs off, etc.

author: jdragoset
author_rank: Frequent Contributor
timestamp: October 23, 2020, 10:33:04 pm
content: Even with correct plug polarity, everything inside will be line-hot with the switch off, through the filament string.Best to use an isolation transformer.

author: bdunham7
author_rank: Super Contributor
timestamp: October 23, 2020, 10:39:04 pm
content: Quote from: jdragoset on October 23, 2020, 10:23:38 pmThese were the types of units that lead to the widespread use of isolation transformers in the first place. It is sort of a common minimal design, except it has one more tube than necessary.

author: rvalente
author_rank: Frequent Contributor
timestamp: October 24, 2020, 03:00:40 am
content: In portuguese we call this topology as "rabo quente" or literally "hot tail" as if your ass were on fire..

author: Scottman
author_rank: Newbie
timestamp: October 27, 2020, 12:24:28 am
content: Sorry, I should have written Packard-Bell. My old age is showing.

author: Scottman
author_rank: Newbie
timestamp: October 27, 2020, 12:29:06 am
content: I previously found a similar document on eBay and received it two days ago. It's a nice add to the radio. Thanks again.