Component ID - Page 1
Forum section: electronics / beginners

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 04:34:09 am
content: I'm restoring a 1981 Radio. I found this capacitor looking thing with 3 pins. After some research I think it's a ceramic bandpass RF filter. It has sticky white stuff on it. Do you think it's gone bad?In either case the code on it is PFWe2. PF is power factor I believe but I can not find out what the WE2 means. If I were to replace it what rating would I need to search for?

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 04:36:22 am
content: Almost forgot to upload a pic.

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2023, 04:59:09 am
content: Quote from: CircuitQuest on October 10, 2023, 04:34:09 amI think it could be a IF filter. Usually those have a frequency written on them though. Usually 455Khz or 10.7Mhz in a standard AM/FM radio. What does the silkscreen on the PCB say?I wouldn't call it bad just because of the sticky stuff. What's the make and model of the radio? You might be able to find a schematic or manual for it.

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 05:11:55 am
content: Quote from: Kim Christensen on October 10, 2023, 04:59:09 amModel is a Sanyo M1700FWow, I literally just found the schem.https://imgur.com/a/ddem3OV

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 05:15:11 am
content: CF1 in the schem is a filter. Now I'm new to all this. I can't find any filter with PFWe2. Can I substitute with another more modern filter just incase I decide to replace it.

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2023, 05:23:48 am
content: Does the radio work on AM and not FM? Because it looks to me like both CF1 and BPF1 are only used for FM.ie: If the radio doesn't work on AM, then there are other problems that should be looked at before messing with that filter.

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 04:20:14 pm
content: Quote from: Kim Christensen on October 10, 2023, 05:23:48 amFM works fine. On AM there are 3 stations 590khz 640khz and 680khz (Strong output stations) that are not showing up or if one does it's very very faint. My other radios pick up those stations with no issues.

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2023, 04:55:23 pm
content: Then those filters (CF1 and BPF1) are OK and are best left alone.Check the DC voltages on the pins of IC1 (uPC1018). Notice how they are labeled AM & FM in the diagram. The expected voltage depends on what mode the radio is switched to. It would be relatively simple to check all the "AM mode" voltages on IC1. Don't worry if they are not exactly the same, but they should be within apx 10% of what's labeled on the diagram.

author: CircuitQuest
author_rank: Contributor
timestamp: October 10, 2023, 05:45:36 pm
content: Quote from: Kim Christensen on October 10, 2023, 04:55:23 pmThanks. Will do.Also I noticed that there are some capacitors connected to the chip on the AM side. I'm no pro but would recapping those help as well?

author: Kim Christensen
author_rank: Super Contributor
timestamp: October 10, 2023, 07:35:04 pm
content: I'm generally not a fan of shot-gunning parts. The exception to that would be electrolytic capacitors in faulty switching power supplies.I personally prefer to find the actual fault first. I've helped people in the past who'd shot-gunned a bunch of parts, but by doing so, they introduced extra faults to the circuit. I guess it's OK if you're careful, have quality parts, and have much better soldering skills than fault finding skills. So it's really a matter of preference.