Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

Bo-Lennart wrote:

------------------

Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that
-14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc.
If I take out the board labeled B15, the -14Vdc is stable. And I can use
the instrument as a AC-rms voltmeter. No problem. But something happen
the I re-plug the board B15. The B15-board have something to do with
the CCIR-filter (I guess).

But I need a service manual to find out.


** I doubt that it would be much use.

Some component pulling current from the -14V rail to ground on that PCB is drawing way too much. Likely culprits include zener diodes, bead tantalum electros and low voltage ceramic caps.
However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.

If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.



..... Phil

Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

Den torsdag 8 mars 2018 kl. 06:35:58 UTC+1 skrev Phil Allison:
Bo-Lennart wrote:

------------------

Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that
-14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc.
If I take out the board labeled B15, the -14Vdc is stable. And I can use
the instrument as a AC-rms voltmeter. No problem. But something happen
the I re-plug the board B15. The B15-board have something to do with
the CCIR-filter (I guess).

But I need a service manual to find out.


** I doubt that it would be much use.

Some component pulling current from the -14V rail to ground on that PCB is drawing way too much. Likely culprits include zener diodes, bead tantalum electros and low voltage ceramic caps.
However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.

If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.



.... Phil

Hi Phil---
Thanks for Your reply.
Some nice guy send me schematics of the power supply board (B16) and board B15.
Was that You???
I checked the Board B15 and found 3 shorted tantal-capacitors, C551, 548, 550.
Changed these capacitors solved the problem.
But there are some more problem with the instrument. In the 3 lowest range 300, 100, 30 micro Volt, the pointer of the movement is not stable. So I will
continue foult-finding. The final problem seems to be in the board B11. This board includes both divider and amplifier. With combinations of these divider and amplifier gives the 15 ranges of +50dB to -90dB.
OK, thanks once again for Your reply. I will continue the foult-finding.
Best regards from SWEDEN
Bo-Lennart Karlsson

On Tuesday, March 13, 2018 at 9:07:44 AM UTC+1, Bo-Lennart wrote:
Den torsdag 8 mars 2018 kl. 06:35:58 UTC+1 skrev Phil Allison:
Bo-Lennart wrote:

------------------

Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that
-14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc.
If I take out the board labeled B15, the -14Vdc is stable. And I can use
the instrument as a AC-rms voltmeter. No problem. But something happen
the I re-plug the board B15. The B15-board have something to do with
the CCIR-filter (I guess).

But I need a service manual to find out.


** I doubt that it would be much use.

Some component pulling current from the -14V rail to ground on that PCB is drawing way too much. Likely culprits include zener diodes, bead tantalum electros and low voltage ceramic caps.
However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.

If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.



.... Phil

Hi Phil---
Thanks for Your reply.
Some nice guy send me schematics of the power supply board (B16) and board B15.
Was that You???
I checked the Board B15 and found 3 shorted tantal-capacitors, C551, 548, 550.
Changed these capacitors solved the problem.
But there are some more problem with the instrument. In the 3 lowest range 300, 100, 30 micro Volt, the pointer of the movement is not stable. So I will
continue foult-finding. The final problem seems to be in the board B11. This board includes both divider and amplifier. With combinations of these divider and amplifier gives the 15 ranges of +50dB to -90dB.
OK, thanks once again for Your reply. I will continue the foult-finding.
Best regards from SWEDEN
Bo-Lennart Karlsson

Hi Bo and everyone else reading,

I'm looking for the service manual / schematics for the very same device. If anyone has them on hand and could forward them that would be reall helpful.

Thanks!

On 2020-04-30 19:17, wrote:

Hi Bo and everyone else reading,

I'm looking for the service manual / schematics for the very same device. If anyone has them on hand and could forward them that would be reall helpful.

Thanks!


For $5 the PDF is available:
https://www.manual-buddy.com/p/sennh...ce-manual.html

Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

Hi....I bought a service-manual. But I can share it with You. I've it as a PDF-file. Size= 12,5MB. I'm not shure if the e-mail-program can handle this size. But I will make it a try.

Bo-Lennart Karlsson
Falun, SWEDEN

Den torsdag 30 april 2020 kl. 19:17:52 UTC+2 skrev :
On Tuesday, March 13, 2018 at 9:07:44 AM UTC+1, Bo-Lennart wrote:
Den torsdag 8 mars 2018 kl. 06:35:58 UTC+1 skrev Phil Allison:
Bo-Lennart wrote:

------------------

Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that
-14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc.
If I take out the board labeled B15, the -14Vdc is stable. And I can use
the instrument as a AC-rms voltmeter. No problem. But something happen
the I re-plug the board B15. The B15-board have something to do with
the CCIR-filter (I guess).

But I need a service manual to find out.


** I doubt that it would be much use.

Some component pulling current from the -14V rail to ground on that PCB is drawing way too much. Likely culprits include zener diodes, bead tantalum electros and low voltage ceramic caps.
However, I would clean and inspect the board first; a loose screw, tiny solder blob or metal fragment would do the same thing if lodged in a bad place.

If you power the -14V from a bench supply, localised heating or a bit of smoke might direct your attention to the right area.



.... Phil

Hi Phil---
Thanks for Your reply.
Some nice guy send me schematics of the power supply board (B16) and board B15.
Was that You???
I checked the Board B15 and found 3 shorted tantal-capacitors, C551, 548, 550.
Changed these capacitors solved the problem.
But there are some more problem with the instrument. In the 3 lowest range 300, 100, 30 micro Volt, the pointer of the movement is not stable. So I will
continue foult-finding. The final problem seems to be in the board B11. This board includes both divider and amplifier. With combinations of these divider and amplifier gives the 15 ranges of +50dB to -90dB.
OK, thanks once again for Your reply. I will continue the foult-finding.
Best regards from SWEDEN
Bo-Lennart Karlsson

Hi Bo and everyone else reading,

I'm looking for the service manual / schematics for the very same device. If anyone has them on hand and could forward them that would be reall helpful.

Thanks!

What is Your e-mail? I only got ".

On 5/1/20 12:29 PM, Bo-Lennart wrote:
What is Your e-mail? I only ".

His email is:


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

Sorry, I can't send e-mail to You. It say, invalid address.
I . Is'nt that the right address?

Bo-Lennart Karlsson
SWEDEN

Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN

My mail is:

On Saturday, May 2, 2020 at 9:39:57 AM UTC+2, Bo-Lennart wrote:
Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN


Thank you very much Bo!
We spent some more time looking for the manual the other day and found it for sale on two websites. Since we got a bit impatient and it only was 5$, we just decided to buy it.

So, thanks again for offering your help! I hope you were successful with the work you were doing on your UPM 550

On Saturday, May 2, 2020 at 10:57:58 AM UTC+2, wrote:
On Saturday, May 2, 2020 at 9:39:57 AM UTC+2, Bo-Lennart wrote:
Den onsdag 7 mars 2018 kl. 18:25:00 UTC+1 skrev Bo-Lennart:
Have a SENNHEISER UPM 550-1 (audio level-meter). My problem is that -14Vdc from the power-supply board is goes upp and down to nearly 0 Vdc. If I take out the board labeled B15, the -14Vdc is stable. And I can use the instrument as a AC-rms voltmeter. No problem. But something happen the I re-plug the board B15. The B15-board have something to do with the CCIR-filter (I guess). But I need a service manual to find out. Maybe someone out there, know exactly what's wrong here.

Best regards from SWEDEN
Bo-Lennart Karlsson
Falun, SWEDEN


Thank you very much Bo!
We spent some more time looking for the manual the other day and found it for sale on two websites. Since we got a bit impatient and it only was 5$, we just decided to buy it.

So, thanks again for offering your help! I hope you were successful with the work you were doing on your UPM 550

Oh and sorry for the confusion with the email address. Apparently it was shortened by the forum.