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
Tillykke med dagen, Søren !Det er en fornøjelse at se den måde, du arbejder på og din stædighed er misundelsesværdig.
Martin
Tillykke Søren
Det er særdeles spændende at se din BM4400 og din iver på succes. Du skal nok komme der. Keep on rocking!
Dillen: Tillykke med dagen, Søren !Det er en fornøjelse at se den måde, du arbejder på og din stædighed er misundelsesværdig. Martin
Martin, stubbornness can be a virtue, and in Søren’s remarkable case, an unquestioned one!
Jeff
Beogram 4000, Beogram 4002, Beogram 4004, Beogram 8000, Beogram 8002, Beogram 1602. Beogram 4500 CD player, B&O CDX player, Beocord 4500, Beocord 5000 T4716, Beocord 5000 T4716, Beocord 5000 T4716, Beocord 8004, Beocord 9000, Beomaster 1000, Beomaster 1600, Beomaster 2400.2, Beomaster 2400.2, Beomaster 4400, Beomaster 4500, Beolab 5000, Beomaster 5000, BeoCenter 9000. BeoSound Century, S-45.2, S-45.2, S-75, S-75, M-75, M-100, MC 120.2 speakers; B&O Illuminated Sign (with crown & red logo). B&O grey & black Illuminated Sign, B&O black Plexiglas dealer sign, B&O ash tray, B&O (Orrefors) dealer award vase, B&O Beotime Clock. Navy blue B&O baseball cap, B&O T-shirt X2, B&O black ball point pen, B&O Retail Management Binder
Happy Birthday Søren!John
Thank you for all the congratulations, now back to the BM, it seams to be as stubborn as I am, but lets see who is the worst, I was, when I opened her, convinced that she was just a dirty old girl, I'm slowly changing my opinion, I think he is a grumpy old man, maybe my soul mate.
Here my software oscilloscope
The signal generator
My idea about connecting the oscilloscope was written without thinking, of course one cant connect power AC or DC direct to a computer without knowing how much, Well, I have something to play with and maybe learn from, at least I can bring the signal generator to good use.
After my siesta, I will go on with the fun, stay tuned, and thank you for the help guys, much appreciated.
Collecting Vintage B&O is not a hobby, its a lifestyle.
Grumpy old man, eh? And both Danish. Love the analogy, two “lions in winter” sparring. Know this, you have the distinct advantage as your grumpy 4400 can not move or hide and you have all those marvelous tools to uncover the mystery of the lack of volume.
I must ask what did you learn from your oscilloscope readout?
Just one day too late, but congratulation Søren! I have been following this thread from the beginning and I am sure you will fix your beloved BM4400 with all the help from the technicicals on this forum. Go for it and keep us updated. Sometimes its too technical for me, but there is still progress in the project. After all you will get a BM which will play for decades. Don't give up!
Working: Here the values from measuring VAC on the speaker output speaker 1. Only Tape 1 ON.
I then changed to a strong FM station, the values shown is nearly max. as they go up and down. Only FM is ON, in balance and Stereo light on.
Here pic left channel, with TP values Left and Right, Measured with only Tape1 ON
Søren Mexico: I then changed to a strong FM station, the values shown is nearly max. as they go up and down. Only FM is ON, in balance and Stereo light on.
Is that with the speaker loads connected as well?Earlier when you were measuring the voltage (signal) level at the pre-amp outputs (TP107 and TP207) you were getting around 1.5 volts there I thought.Is that still the case? I know I am stating the obvious but with the output voltages as you have measured compared to the earlier pre-amp outputs, it looks like the output amplifier is not doing its job.
No speakers connected
I'm at a ???, dont know what to do here, if no good advises turns up, I'll have to desolder the TIP transistors, and check them one by one, but if I start to move the wires connecting to the TIPs again, I'm afraid they may break, they are holding up until now, but who knows. Off to bed tomorrow another day.
Please, try using the amps on their own before doing anything else!
This will rule out the power amp section if anything. I feel there's a problem in the preamp section, somewhere and your testing method always includes it. I'd test each section separately, not the receiver as a whole.
I don't understand your logic Søren
Night!
Jacques
chartz: Please, try using the amps on their own before doing anything else! This will rule out the power amp section if anything. I feel there's a problem in the preamp section, somewhere and your testing method always includes it. I'd test each section separately, not the receiver as a whole.
Completely agree with this
//Bo.A long list...
Bos00: chartz: Please, try using the amps on their own before doing anything else! This will rule out the power amp section if anything. I feel there's a problem in the preamp section, somewhere and your testing method always includes it. I'd test each section separately, not the receiver as a whole. Completely agree with this
Thank you gentlemen, so I connect a sound source to the C132, Jacques you mentioned earlier, shielded wires to the C132, shield to ground ????.
The sound source ??, can I use my computer or do I use a phono preamp, I have a preamp with a gain adjustment.
As I'm a little nervous about this, How much VAC or VDC can I connect there ???
Jacques, bear with me, I'm doing this for the first time in my life, my knowledge of electronics is very limited, and I dont want to destroy the work I have already done on this unit.
Søren, you know I have been following your amazing efforts since day zero. Stripping the 4400 completely was very brave to say the least!
You also helped me with my CD50! Who would I be to criticize?
Yes you have correctly understood what I was suggesting. I'd use a preamp, and a potentiometer in between, for safety matters. Sensitivity should be about 500mV peak to peak I guess. You will not destroy anything!
And at least if you can get nice music and go loud without any distortion, you'll know the power amp section works. This will be a reward to your painstakingly done work.
If you have that pc-scope software installed, you can use it as a source, it "has built-in potentimeter" as well
blah-blah and photographs as needed
....and even though you have enough to do on this task already, please take some pictures :)
chartz: Søren, you know I have been following your amazing efforts since day zero. Stripping the 4400 completely was very brave to say the least! You also helped me with my CD50! Who would I be to criticize? Yes you have correctly understood what I was suggesting. I'd use a preamp, and a potentiometer in between, for safety matters. Sensitivity should be about 500mV I guess. You will not destroy anything!
Yes you have correctly understood what I was suggesting. I'd use a preamp, and a potentiometer in between, for safety matters. Sensitivity should be about 500mV I guess. You will not destroy anything!
You did not understand my logic Jacques, the trues is, there is non, after measuring and not understanding the results I got totally lost yesterday.
Back on track, if now my FS and her sisters can leave the house and stop bothering me with stupid questions, I can start working
Oh yes, stupid questions from non-believers. Not much one can do about that.
"What's that thingy with colour rings on it?"
"Is that three-legged thing a microchip?"
"How come music comes from that?"
"Hey what do those figures on your yellow box mean?"
"You will clean the bright stains on the floor, right? Will they come away?"
Here the connection I made, from computer the yellow plug, to red jack, red wire to C132, where I disconnected the green wire coming from preamp.
The DMM is connected to the C132, measuring AC coming from the computer. Volume here set at 50%.
Now I put the signal generator to 60 Hz, and full amplification, volume at computer 0 and will go slowly to 50%
I then connected the DMM to C132, volume on the computer to 0, going slowly up to 50%. and get this reading,the DMM in the pic is connected to the speaker2 output, speaker1 is connected to a 4 Ohm speaker, I can connect the DMM to C132 and get the same reading, or to P11 pin 3, same reading everywhere. Which means that I have no amplification, the signal just goes straight through without amplification. I can play a CD and get the same result, same in as out.
Going through the TR 112, 113, 114, seams OK measured on board, but then I checked the R163, 22K ohm, normally I should not tell you this, but I am a stupid but honest man, instead of 22K I put a 22 Ohm there, blind, stupid and careless, of course the k on my DMM is tiny, but even so, stupid.
Easy mistake so don't feel dumb. I would feel relieved to have found something that can explain the problem. So did you put 22 Ohms in for both R163 and R263? Also do you have 22K Ohm resistors to put in now for the fix?
Had 22Ks and put them in, but now we are back at lane one, the RL1 is activated as soon as I connect Tape, phono or fm.
I connected the wire to C132, with a hook clip, Took of P11, tape1 ON, overload light shortly and RL1 pulls, same with P12, both off RL1 do not activate.
I think I am following you - You separated the 4400 preamp from power amp at C132 and C232, right?
You also had 22 Ohms for both channels (R163 and R263), right?
Would it be worth it to eliminate the preamp as a suspected culprit? --- Do you have a stand alone power amp you could route the 4400 preamp out (where you made the test connection) and verify the preamp is working fine?
When you say "as soon as I connect Tape, phono or FM", you mean turn the 4400 on by activating one of those buttons, right? If so, you are saying that the RL1 activates when power is applied...which means the problem surely is in the power amp section. You might have to go through each component in the power amp one at a time again to verify the value and that the component is oriented correctly (as currently installed).
Yes, yes, and no I have no power amp. But when we tested the preamp, with the volume turned down, there was no current going to C132, only with volume turned up I got current.
I will go through the components again, and check all resistor values.
Will be back tomorrow
At 22 ohms you had a short! Like a potentiometer almost at zero...
Yes that kind of mistake can happen, so well done finding it!
No wonder the output was so weak...
Now try with some music please - why don't you want to do that? - with BM preamp disconnected. Please unsolder those C132/232 and solder other ones with longer legs at the amp input. Then see whether the music flows through speakers (forget that silly computer scope) with the beacon off and the relay at rest.
If this test succeeds, then the preamp is at fault.
By the way, it seems to me - after your pic - that you injected the signal after C132: this is wrong, it should remain connected to the input stage! Did you actually unsolder it at all?
@ Jacques
I did not unsolder the C132, but the green wire coming from the preamp, which is the positive side of C132, the negative side goes to base on TR112. I soldered the positive wire from the RCA where the green wire was before.
But if you read my post after changing the R 22K, you will see that the RL1 is now activated when turning ON the BM, the RL1 interrupts the 35 V+- feed.
I did play music through the speakers, (a CD from the computer).
After my bath and breakfast, I'm going back to the BM, to go through the components again, if no more failures are found there, I will go through the solder side with a 10 x thread counter.
Checked all resistors, ohms and where I could not get a clean reading, checked the color, codes. Checked diodes and cathode direction, checked all transistors for type and BCE placement. All seams OK. Checked solder side with 10 x magnifier, cleaned solder side one more time.
Powered on RL1 pulls. Connected over variac, went to 60VAC, as the fault switch is triggered from speaker out I checked P11 pin 3, left channel, gets - 90mVDC, checked P12 pin 3, right channel, gets +15VDC.
Desoldered 0IC200 and 0IC201, checked again, get -15VDC, desoldered leg C on 0IC203, checked again P12 pin 3 now +900mVDC..
Checked the TIP142 and 146 with diode tester, seams OK.
Just my intermediate congratulations to your work. You have not been screwed up in the beginning by the screw shaped mine in your BM 4400 and you teach us much about accurate work and its benefits.
Søren Mexico: Checked all resistors, ohms and where I could not get a clean reading, checked the color, codes. Checked diodes and cathode direction, checked all transistors for type and BCE placement. All seams OK. Checked solder side with 10 x magnifier, cleaned solder side one more time. Powered on RL1 pulls. Connected over variac, went to 60VAC, as the fault switch is triggered from speaker out I checked P11 pin 3, left channel, gets - 90mVDC, checked P12 pin 3, right channel, gets +15VDC. Desoldered 0IC200 and 0IC201, checked again, get -15VDC, desoldered leg C on 0IC203, checked again P12 pin 3 now +900mVDC.. Checked the TIP142 and 146 with diode tester, seams OK.
so we have the following situation left channel is working fine (except low amplification?) but heavy problems on right channel?
If you check the TIP14x Darlingtons keep in mind that they have a protection diode build in from (C to E). see here Check whether these diodes are intact.
Reading the whole service manual (page 5-5 )gives some hints about the AC Voltages we should get. This helps to determine the function of the preamp. (and later the power amp too)
Everything in linear mode, bass and treble set to '0' (middle position), balance to middle position, volume set to maximum. P11 and P12 unplugged!
Injecting 200mV AC at 4TP101 (Tape 2 Left In) should result in 166mV AC at 5TP100 and 443mV AC at the end of the preamp at 5TP107.
You should get the same at the right channel.
If you get more or less AC at 5TP100 you should be able to set the correct readout with the corresponding poti R119.
If the preamp is working you can use it later for the testing of the power amp.
I suggest you try it this way so you can use your beomaster low power parts for testing the power amp with music, signal from PC or whatever later.
Ralph-Marcus
Will check this next weekend, going out in the province for one week to work.
Back in the saddle again, the province work took a little longer than expected, and some other jobs had to be done when I came back.
After doing my paper work today, I took a look at the BM, but the spirit was not there, so it stayed by the look over a cup of coffee.
I have some spares for the BM that arrived from the north side of the boarder, so tomorrow I will be working on it, I promise.
¡Buena suerte!
Desoldered and checked all the TIP 142, 147, and the TR 200, all OK compared to new ones. connected it all again, still got the 15 Vdc at P12 pin 3,with the Variac at 60 Vac.
Desoldered 0IC203 and 200 C leg, 15 Vdc still there.
I will have to find out where they come from, been at it for 2 hours now, but no luck, tomorrow back again
Hi Soren,
have you checked also the integrated protection diodes of the TIP142/147 (see the link from my posting march 18th) ?
At March, 16th you showed an excerpt of the power amplifier circuit with voltages. can you check the voltage at both Emitters of TR 112/113 and 212/213 ? Should be done at full 110V, so disconnect the resistor R47 from connection where it meets R46 so that the protection circuit doesn't react on the right channel
Check all the TP's mentioned at page 5.5 in the manual for 4TPxxx and 5TPxxx and keep an eye to the reference point! For example check TP209 to be 2V with ground at -35V ! This is the voltage across R258. Across D202 you should get 2,7V. Across D203 you should read ca. 12V.
Keep us informed :) and good luck!
Hi Ramabo
I'm at it now, I disconnected P11 and P12, Variac at 60Vac, at TP 107, 207 I get 1.3Vdc, at TR 112 E I get 0.7 Vdc, at TR 212 E I get fluctuating dc up and down fast. Desoldered C232,233, and TR 212, they are all OK measured off PCB, will put them in again and try as you told me, but I'm nervous about cancelling the fault switch.
All TIP 142,147 are OK, also the diodes in there shows, no problem, Tip 142 E-C, 0.456, C-E "0", Tip 147 C-E, 0.486, E-C, "0" .
Small rest required, kitchen duty, for 1 hour, will be back soon.
Now presenting BM 4400, type 2419, Ser. No. 1408008, playing since one hour, FM Oldies but Goldie's,
Found the failure, a broken track between TR 212 E and TR 213 E, I was afraid of connecting without the fault switch, so I tried one more time with P11 and P12 connected and started, again, at TP 207, checking against left channel, checking Vdc after each component, and at TR 212 got 0.6 Vdc, but at TR 213 E I got 5 Vdc, should be the same, checking track and soldering, the TR 213 E was now loose from PCB with solder point and piece of track, must have given connection once in while, because I have been checking this connection various times with no power on the BM, but desoldering I was probably fumbling around there a little and the track now came totally loose.
This failure has cost me I dont know how many hours, at the point of giving up, but more than 8000 hits on this thread made me go on and on.
A big thanks to Martin for providing 2 complete sets for the amplifier channels, for free, and a big hug and thank you to the guys that helped, without you, I would not have gotten there. And not to forget Jeff (Piaf), who always kept my spirit up.
THANK YOU,
Will be back with more after final tests and adjustments, and of course assembling.