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
Craig,
I think this BC549BTA ia a great alternative to the BC113.
Sorry for the late answer btw...
Charles
Craig: Charles Would BC549BTA be an acceptable replacement.....it looks quite close to me? Craig
Would BC549BTA be an acceptable replacement.....it looks quite close to me?
Craig
Ok.....moving on, Peter called on Saturday and dropped off his Beomaster 5000 tuner to enable me to make some comparisons around voltage levels, I'm busy doing just that. I have to say Peters tuner is far more sensitive than mine and can pick up more stations. I have tuned both sets to the same channel and taken the measurements at the same time....I have scribbled them down and will tidy them up before posting tomorrow....
Voltages measured so far...the voltages measured within Peters machine in parenthesis
Check the thin wires to the coils.
Martin
Cheers Martin....thought you may be looking in from time to time ;¬)
Checked the thin wires in the front end coils and also checked them against peters unit and all are soundly connected, tuned both receiver's to the same channel again and had a probe around with my new scope.....it's going to take a little getting used too, lots of features that are a bit of a mystery to me right now.....however I connected both up to the scope from the test point at AF121/5 (69) the circuit above and got this trace, peters machine is the top trace...both machines sounded ok during the test.
I also noticed during the above that my unit would briefly jump up in volume and clarity, the tuning meter cracks hard upscale....and then it all drops back down again?
Ok.....following on from advice received from Solderon (Nick), and Martin I focused some more attention on the front end....I have discovered that when I touch one of the transistors inside the can with a screwdriver the tuning meter leaps up to a healthy level and the volume and clarity of the station I'm tuned to increase accordingly, its an appreciable increase in reception. I tried the same with Peters machine and there is no difference in the quality of reception or deflection of the tuning meter.....so I'm reasonably confident i'm onto something, my problem is identifying which of the three transistors it is...…...
The red line identifies the tab in the middle of a coil that connects to the offending junction.....the circle in this pic shows the transistor itself, can anyone identify him and suggest an equivalent?…….I can always winkle it out anyway and maybe read any markings, but I would prefer to be sure, also when I touch this tab the low voltages I have been measuring around the muting and stereo pots increase significantly too.
Opened one of mine, dont know if it can help
Collecting Vintage B&O is not a hobby, its a lifestyle.
The drawing
Soren....Thanks for that, however looking at the picture and schematic I can see yours is a different version of the 5000 to mine, the transistor numbers and the schematic drg number differ from the one I have, mine is a 2005 model.....they look to be wired up differently. I'm having difficulty identifying the coils so cant determine which transistor is which...yours all seem to be metal can types too, where only one of mine is in that style.
I have 2 more, 1 is easy to get at will come back
No. 2
drawing
Soren
Can you confirm your getting 11.5v on your AVC to the base of AF106 for me....?
I think I have identified the transistor I'm touching with my screwdriver as TI401 and not AF106 as I was expecting, I have taken some measurments around it...but I dont have the 11.5v to the base of AF106 which is the first amplification for the antenna? oddly when I measure this point on Peters machine, which works fine...I dont get 11.5v either?
Close up of the meter and now functioning stereo lamp....I had to adjust the stereo pot at the back to get it to kick in....
The muting function is also working now.....though I haven't adjusted it correctly as yet
Well...with a heavy heart I have to report that the whole thing has come tumbling down again! everything worked fine for 2 or 3 hours and it went down like a sack of potatoes! to be honest deep down I sort of knew it wasn't the end of the road with this....problems rarely evaporate into thin air, they have to be tracked down and resolved. So this morning I set too with soldering iron in hand and removed the front end....and just to be sure I removed Peters front end too (sorry Peter I will put it back carefully I promise )….and fitted it into mine the expected transformation took place, So now I'm sure where the problem lies.
Its a lot easier to work on out of the chassis anyway.....I have been advised by Nick that AF106 is the most likely culprit, so now I have the unit in hand I can follow the circuit a lot better....also I have been able to tease it out of the housing enough to confirm its type number....and of course it doesn't say AF106!....wouldn't have it any other way! it says SF8636...…..traced the circuit out around it, bit rough I know.....but bears no resemblance to the diagram I have in the manual.....
Managed to unsolder two of the legs from inside the can, it's very difficult to get at and the third leg will be a challenge....but 2 off is enough to get my transistor tester hooked up.....
And its a JFET...so the new AF106 in the top of the picture is of no use.....this all explains why I was having so much trouble identifying these little devils, I say this because it looks like my TI401 has a very similar type number from what I can make out.
Looking back at the diagrams Soren has posted for me mine is starting to look awfully like the 8050039 circuit! So gentlemen.....once again I'm seeking guidance as to the most appropriate replacements for these, anyone got any ideas?
So which one you need Craig? I have a bunch of old IF transistors here I can check.
That would be great....To start I'm looking for what could be 2 0ff SF8636 or the equivalent of, I definitely need one could be 2 as I think the TI401 transistor in my drawing is also a SF8636. As for the third one TIXM203 in my drawing I'm not sure...It has 4 legs and not 3 as per the description at the bottom of the circuit drawing in my manual....all a bit puzzling right now ;¬)
Searching I found that some enthusiast has been changing SF 8636 with BF245B
Thanks for that...is it readily available?
Not over here, maybe over there in Brexit land
https://alltransistors.com/mosfet/transistor.php?transistor=1230
https://www.ebay.de/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=bf245b+jfet&_sacat=0
http://www.nteinc.com/specs/100to199/pdf/nte160.pdf
Thanks Charles and Soren.....looks like I need 2 of these, winkled out the component identified as TI401 in my manual and confirmed it is actually a SF8636 so two JFETS, Both are measuring up good on my tester but as we all know with an intermittent fault this isn't surprising,
The only remaining transistor in the front end is the oscillator, I'm thinking if this was faulty I wouldn't get any signal therefore I'm reluctant to pull it, unless anyone can advise me otherwise?
Ohh...and I have replaced Peters front end successfully , the biggest task was getting the dial cord back correctly!
No problem - I have complete faith in you and if it gets your Beomaster working, it is certainly worth it. That is why I dropped it down!
Peter
Thanks for that vote of confidence ;¬)
Ok....the replacement JFETS turned up today, put them on my tester and of course the pin outs are different, wouldn't have it any other way. Never the less set to with the soldering iron and with a herculean effort got the first one soldered in place, such a tight area to work in with multiple connections all wanting to fall off all the time..
that's TI401 installed, the easiest one as it turns out...AF106 was much harder with the hair wires to reconnect, couldn't get a good picture of it which illustrates how difficult it was to get in, you can just make out two of the legs with brown sleeve coming out of the right of the central metal screen...
With a deal of excitement I replaced the front end and soldered the connections back on....powered up and "Jackpot" crystal clear solid reception over a much wider range of stations! I know I have been here before and after a couple of hours was disappointed....so I'm reluctant to shout from the roof tops, but on this occasion I have actually done something that has produced a result and not some random chance event like last time......still I will leave it on test a while and report back ;¬)
Well done! I will keep my fingers crossed!
Left her on for 3 hours last night and all was good, powered up again this morning and everything is still good......time to box everything up! Soren...I owe you a cigar for that schematic, helped me confirm I was dealing with JFETS ;¬)
Glad I could help. Impressed of your solder work in that component jungle, BTW the 3 BM 5000 I have here came from Henrik (Square4) . Interesting to see that all 3 drawings are different and correct for the BM they are supplied to, whereas on other BMs I have repaired I normally find discrepancies.
This just shows how far the engineers went with quality in these marvels, it has been interesting following your thread and I hope for more to come. Compliments also to Peter for going out of his way to help.
If we ever meet in person remember the cigar
Thanks for that Soren...always remember its the support from people like you, Charles, Martin and Nick who make my endeavours possible....and of course Peters contribution was invaluable, I have the tuner playing right now as I type this and it still sounds excellent...….I will put everything back together over the week end and post a picture....and by the way my soldering within the front end is not pretty to look at, but its quite solid ;¬)
Regards Craig
I didn't help as much I wanted Craig, i've been on and off lately... Glad you got it back right! Congrats!