ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
On quite a few occasions the B&O part number for a capacitor is very brief on details.
A classic example: Service Manual BeoMaster 2200 - Tuner Section of Unit - B&O capacitor P/No. 4330001 Full Description 9 pF Cer.
No tolerances and importantly, no max. Voltage......!! How the hell do you know what to replace it with.....??
Do you just have to retrieve the original from the PCB, put it under magnification and hope to find the missing info. printed on it or is there another, empirical method of working out the max. voltage...??
TIA
The voltages (and usually tolerances) are always specified for electrolytics, otherwise only when they have some importance.
Ceramic & foil capacitors typically always have a much larger rated voltage than what is needed. The exceptions are mostly in high voltage sections in televisions, and then you will find the specs in the service manuals - if you have the full manual, they are often omitted in schematics simply to keep them readable.
Ceramic & plastic caps are also usually much more accurate than electrolytics, so tolerances aren't specified too often. With them, it either doesn't matter, or the variations can be compensated with some adjustment. In your example, it's quite possible that you would need to realign the tuner and/or IF sections for best performance, if you have to replace that particular cap.
--mika
Ozymandias: How the hell do you know what to replace it with.....??
How the hell do you know what to replace it with.....??
It's a common misunderstanding that service manuals will tell you how to repair the thing.The service manual will usually tell you how the thing was made and how to open it.Indeed that's how B&Os and many other brands service manuals work.It will not turn you into an electronics repairer. Rather it assumes the person reading the manual to havea solid amount of electronic skills, education and experience in order to service things so will typicallynot state info that is obvious to the tech guy.Any trained electronics guy will be able to tell which component specs are important in acertain circuit, max working voltage indeed falls into that category.Looking at what the factory has fitted will also give a good reference.
My experience tells me that tuner faults in a Beomaster 2200 are very rare.Most faults that look like tuner faults are in fact caused by aging and dried-out capacitorsin the power regulator circuit. Always the first thing, I replace in Beomaster 2200s.
Martin