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
I actually was certain the problem was with the P21 cable assembly so I swapped it with a spare I have. Thinking the problem was solved, I returned the Beomaster to the SC80 cabinet and was ready to enjoy the 8000 system again. After a few minutes of happiness though, the left channel dropped out. Here is the P21 cable assembly.
I went back to the bench with the BM8000 once more and was determined to find the problem source. This time I noticed the P15 connector could be moved and return the missing channel. After experimenting with the P15 connector (rechecking solder joints and the cable wires), I determined that I couldn't fix it in its current state. So I decided to change both the P15 cable connector and the preamp mating connector.
It has now been over four weeks and the Beomaster hasn't failed since this last fix. This goes to show that being a fan of vintage audio often requires repeat visits to fully get these nice machines back to full use.
-sonavor
Very true! Repeat visits are not uncommon.
Just proves how much they want our love and attention!
Very nice replacement components in there!
Menahem Yachad: Very true! Repeat visits are not uncommon. Just proves how much they want our love and attention!
Yes, demanding beasts they are. Gotta love em.
Yes. They do require a bit of attention.
I'm picking up another BM8000 next Monday. What will I find this time?
Jacques
chartz: I'm picking up another BM8000 next Monday. What will I find this time?
Is there a cure for this rare desease?
Where is research standing?
chartz: Is there a cure for this rare desease? Where is research standing?
The only known cure is extreme - You have to move to a remote island that has no electricity. Meanwhile, the research has fallen apart as all of the researchers have contracted the disease and are now actively working on their B&O projects.
I have two spares (defect) that could be used for donor parts in case of.
Brengen & Ophalen
That did no fall on deaf ears Leslie!
Just let me know or else I will throw it in the bin...
Leslie: Just let me know or else I will throw it in the bin...
Don't throw anything into the bin. I have another BM8000 waiting for restoration as well.
sonavor: chartz: Is there a cure for this rare desease? Where is research standing? The only known cure is extreme - You have to move to a remote island that has no electricity. Meanwhile, the research has fallen apart as all of the researchers have contracted the disease and are now actively working on their B&O projects.
Running out of space does not cure the disease, but it does treat the symptoms.
One thing I remember about my own BM8000, the cable(s) from the control panel can affect those segments lighting up. As I was getting mine refurbished I kept seeing the segments come and go. I was wondering if the displays were going out. Once I got the receiver completed though, the segments all worked. That doesn't mean it will always turn out that way but I would hold off on dealing with the displays until the end. One way to check them sooner though is to remove them from the board and check them in a test jig that powers all of the segments. That's what I did with one of the Beomaster 6000 units I repaired.
I'll look into that John, thanks!
A closer inspection of the innards shows that the amplifiers boards were restored at some point, with new capacitors and trimmers. The output darlingtons seem to have been replaced. Not a very clean job I have to say. The rest of the receiver was not modified or restored.
The left amplifier remains completely cold (no sound) with a normal offset voltage. The right amp works but quickly gets lukewarm. I know it should not. It is not a Beomaster 6000!
I'll have to delve deeper into that.
Right, I understood are working on another BM8000. I only mentioned the BM6000 with regard to a jig to test the display segments. On your BM8000, are you getting the two channels through your preamp stage? Just wondering if it is isolated at the output amplifier boards. You might need to recheck the mounting of the output transistors to the heatsink.
And I was referring to the heatsinks of the BM6000, always lukewarm!
haha...too much mixing of Beomasters
Have you come across this?
http://vintage-radio.net/forum/showthread.php?t=110262
Tim is the best!
No, I had never seen that link. Very interesting and quite amazing really. I have wondered if someone with the right know-how had ever recreated one of the B&O processors from the eighties. Now I know.
Thanks
Tim is well known amidst B&O circles in England. He wrote the B&O collector's bible, as well as many articles for Hi-Fi World and Hifi News.
My tatty Beomaster 8000 now almost work. The important bit - the amplifiers work fine. There were really messy repairs, which were supposedly meant to work! Fortunately, the new components (many transistors, all the TIP 141 and 146) were still fine, and I suspect the repair was aborted. In fact, the previous repairman had broken PCB tracks in several points. After repair the power modules work. He (she? nah!) even replaced the trimmers and the caps, which was a good idea!
Two remaining issues: the missing LED segments, and only static on the tuner. Yes John, I checked the small transformer leads!
chartz:Tim is the best!
Consider the hours he must have used for this project, not to speak of the time used before and during the project, thinking about it. I have a couple of times done "impossible" repairs on printing m/cs, reaching sometimes the point where the client declines to pay for my time. But as you have an idea and you are sure the solution is around the corner, you just goes on, not thinking about time and effort (or payment). Some of the members on this forum, has the same attitude as Tim, we never give up, and looks for solutions for the "impossible" . You dont have to be crazy to do it, but it helps.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Crazy eh? Yes, possibly so. But I feel a bit like Steve Jobs in a reverse kind of way, we are the crazy ones, the misfits who believe that ancient devices still have something valuable in their guts, that they still have something to say. They have a soul.
Tim, Martin et al, great purveyors of parts and advice, believe in that too, and keep helping us, day in, day out. Let me thank them for that!
Back to business then.
A change of U264 - I had one spare - has not resolved my tuner issue. No control over input voltage to the varicaps, whilst displaying the whole frequency range.
I feel that I am on my own here.
What are some more details of the failed tuner? You're getting the FM station but not the correct display? Or are you not getting anything from the tuner? I just got a Beomaster 6000 back to full operating condition last night. The last thing I had to do on that one was replace the tuner signal cable (the 2-wire one inside from the tuner board to the processor board) because the cable was bad. So double-check the cable in the BM8000 if you haven't already. Also, the cable from the control panel to the processor board in the BM8000 can start breaking at the board connection. Sometimes it is hard to see that one of those connections is broken. If you are seeing the frequency jumping around it could be that control panel board connection to the processor board. On my BM8000, I finally just detached that cable, stripped new leads and re-attached it.
Thank you John.
Every single wire was duly checked. In fact, they are the first elements I verified. I know about the BM6000 cable, I had the same problem, with the digits displaying 74 MHz or something like that.
I get static (hiss) in manual, and no MPX or multipath signal. Of course, no radio. The galvanometer is good though.
I will have to test the tuner boards.
By the way, what do you say to a TP2 input that has less treble on both channels, along with a narrowed stereo image, than TP1?
The preamp boards were fully re-capped, but it made no difference whatsoever.
chartz: By the way, what do you say to a TP2 input that has less treble on both channels, along with a narrowed stereo image, than TP1? The preamp boards were fully re-capped, but it made no difference whatsoever.
Does the Phono input work okay? If the phono path is fine then I guess I would check out and try replacing 3IC1 OpAmp. You've already cleaned the input level trim pots (3R122 and 3R222), right?
So I'll try replacing the op-amp then, the rest being okay. I was thinking along the same lines here, input electronic switch IC, then op-amp on TP2 line. Still I wonder how a partially defective LF can degrade sound quality that way...
Thanks!
I thought I was about to solve the tuner issue. I found that the tuning voltage was never arriving from the connector to the front end. So I grabbed a magnifying glass and found this.
False hopes... After repair, still nothing but static. I can now see voltage at the right places, but all I can get is Vmax (22V) and Vmin (3V) before and after about 91 MHz. But this time, no zooming of radio stations.
The signal meter stays idle. It is good and the needle responds to voltage from an exterior source.
I did replace the pre-scaler (twice so I'm sure) and the 4013 flip-flops.
We have a shorted TDA1062! The 47Ω protection resistor was duly burnt, but it was difficult to see. A voltage test revealed that.
Mmmm... Don't have that in stock
I'm not sure what caused the internal transistors to burn. It is shorted between PIN13 and ground. What are R6 and R11 anyway?
Is it a fragile chip? B&O fitted a protection resistor for a reason, didn't they? They knew something that we don't!
Right here for you, in France.
http://www.ebay.com/itm/TDA1062-Tuner-FM-CTDA1062-/180788694030
I've bought from him a few times - quite reliable, and has most of these obsolete B&O parts.
Menahem
Hi Menahem,
I've already ordered from him too! Thanks for the link!
Ordered placed! (in fact, double post but I've found something else to say )
One more component to replace. Let's hope it's the last one... There must be some logic here, but I don't see it.
The other transistors appear to be fine. I have tested the coils as well: I had a doubt about L7 but it is fine.
Did you replace those trimmer potis?
I usually let the tuner trimmers well alone. I don't have suitable equipment to handle FM circuits.
The new TDA1062 arrived yesterday. Then again, B&O fitted a protection resistor (R21) for a reason, I'm pretty sure that they knew the failure mode of that Telefunken chip! I think this is a first on the forum!
And the repair is a success!
The tuner now works (as usual, even without any aerial, it pulls in a few stations) and the meter and MPX beacon are back.
Pre-sets work to.
I now have a rather tatty Beomaster 8000 that is fully functional. I need new wood trims (the right one is fine, the reveiver was stocked standing on its left side, oh dear, can you imagine? Well, I sore it! (for Brits only) and the display misses a few segments.
The top is okay, not sctatched or anything, except that someone tried to lift the middle bar with a screwdriver. Sometimes...