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
Hi Everyone,
After doing numerous fixes on my Beomaster 2000 2801 before, I now face a slightly more vague problem. The FM reception seems to be not too great. In principle it works, but most stations are impossible to properly tune (without lots of static).
A few years ago I already replaced all electrolytic caps in the Beomaster plus the film ones that were cracked, but none of the others.
My first guess for the FM-issues was to replace all the potentiometer trimmers (they look horrible) and then check some of the test voltages.
While the machine is open, I was wondering whether you guys advice to also replace some of the other capacitors? I would guess the ceramic ones should still be good, as well as the film ones that are not visually bad, but I'm not sure about the polystyrene ones and the tantals. Especially the latter ones usually go bad at some point, but I'm wondering what your advice/practice is with this.
Any advice?
Thanks!
I don't know the answer, but I do have this list that might help. I scanned the Service Manual with OCR, then went through and compiled a list of all the capacitors and their values. There may be some minor errors that I missed, so let me know and I'll update it. The number at the end of each line is the count of that value capacitor.
Aside from that, if you don't have the service manual, then I'd recommend you get a copy. Oh, and if any of your plastics are broken then let me know. If you look in the What are you working on now thread, you can see what I've been working on.
Beomaster 2000 2801Capacitor Value Number
0,1 μF 10% 250V 40,1 μF 20% 250V 120,1 μF 35V 30,22 μF 10% 250V 10,47 μF 10% 100V 10,47 μF 35V 81 μF 35V 191 9 pF Cer 11 nF 10% 100V 111 nF -20 + 50% 400V 11 nF -20 +50% 400V 81 nF 250V 31,5 nF 5% 160V 11,6 μF 5% 25V 110 μF 10V 510 μF 16V 310 nF 10% 250V 210 nF 20% 250V 110 nF -20+ 100% 40V 710 nF 5% 63V 210 nF-20+ 100% 40V 110 pF 2% 63V 1100 μF 3V 1100 μF 40V 3100 pF 5% 100V 1100 pF 5% 63V 115 nF 10% 250V 4150 pF 2,5% 63V 1180 pF 5% 63V 11-9 pF Cer 32,2 μF 35V 112,2 nF 10% 63V 22,2 nF 5% 63V 320 pF foil 222 μF 6V 222 nF -20 +100% 40V 122 nF 20% 250V 422 nF -20+ 100% 40V 622 pF 2% 63V 122 pF 5% 250V 1220 μF 25V 1220 pF 10% 100V 1220 pF 5% 63V 2270 pF 5% 63V 22t2 nF 5% 63V 13,3 μF 5% 63V 13,3 nF 10% 100V 33,3 nF 10% 250V 13,3 nF 5% 63V 13,3 pF 0,25 pF 400V 13.3 nF 10% 100V 133 pF 2% 63V 2390 pF 10% 100V 1390 pF 100V 14,7 μF 25V 24,7 nF 10% 63V 14,7 nF 5% 63V 14.7 μF 25V 1440 pF 1% 63V 147 nF 10% 250V 147 pF 2% 63V 2470 μF 40V 1470 pF 5% 63V 65000 μF 35V 2560 pF 5% 63V 260 pF foil 368 pF 5% 63V 2680 pF 10% 100V 1680 pF 5% 63V 28,2 pF 0,5 pF 250V 28,2 pF 0,5 pF 400 1Total Number194
Thank you for your reply, I think that list is very useful for anyone working on these! I do have a service manual, which is essential indeed!
I'm just not sure whether all of these need replacing. Especially in the tuner-section I'd prefer to keep the old caps if possible, to prevent having to retune everything completely (I also don't have the equipment for this).
No it is probably not necessary to replace all - would be expensive too! I think a good rule is do as little as necessary.
I'm not having too many issues, but I'm replacing the main electrolytics:
Agreed, those I did replace already a few years back, together with the bias trimpots (can for sure recommend those as well). Will now start with the trimpots in the tuner section, hopefully that resolves my FM tuner issues...
I sent you a personal message about the plastics, thanks for your efforts!
No problem. I'll reply by email to your message.
So, I did recap the tantalums in the beomaster this weekend. I also changed the trimpots in the FM-section.
I also took some measurements and noted very asymetric voltages on the collectors of 2TR10 and 2TR11 in the stereomodulator (6 and 7.4 V). I replaced those with a Hfe matched pair of BC546B's. This symmetrised the behaviour of R and L channels. Furthermore, I replaced the diode bridge generating the 26V supply since I read quite some people have experience with it dying.
Tuned all the trimpots up according to the service manual, except for the Level control and the crosstalk ones. Does anyone know what the procedure for these is (it's not mentioned in the service manual). Level control tunes the necessary IF strength to have the TCA420 switch to stereo mode. Only thing mentioned in the service manual is that for Aerial signal > 5uV, 2TP7 is 5.4V and for Aerial signal < 5uV, 2TP7 is 0V. This seems to suggest that 5uV Aerial should be the threshold for switching?
The cross talk pot I just kept fairly centered for now, does anyone know about this one?
I just hooked the BM up again and it works wonderfully again! The sound also significantly improved, I guess some of the tantals weren't what they used to be anymore... FM works as well. I cannot say what the culprit was, either bad caps, bad trimmers or aged semiconductors, but now it works perfectly again.
Nice!
Is cross talk about separation between left and right channels? I'm not finding much about it either.
How many tantalums did you end up replacing? They're the little red ones right?
edit...
Page 139 says something about crosstalk that may be relevant:
https://www.americanradiohistory.com/BOOKSHELF-ARH/Technology/Stereo-FM-Radio-Handbook.pdf