PSU query...

C

Cursitor Doom

Guest
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg
 
On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg
Click to expand...

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet
 
On Mon, 11 Sep 2023 12:57:59 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet
Click to expand...

Thanks, Erich. This design seems highly unusual to me and it\'s hard to
work out what\'s going on here. I\'m seeing minus 8V on the emitter of
T8 which makes no sense to me. Es gibt keinen sinn! Does negative 8V
WRT GND seem okay to you??
 
On 11/09/2023 14:59, Cursitor Doom wrote:
On Mon, 11 Sep 2023 12:57:59 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet

Thanks, Erich. This design seems highly unusual to me and it\'s hard to
work out what\'s going on here. I\'m seeing minus 8V on the emitter of
T8 which makes no sense to me. Es gibt keinen sinn! Does negative 8V
WRT GND seem okay to you??
Click to expand...

Yes that circuit does need careful analysis but what you see sounds
correct. T7 and T8 keep dry battery separate from the rechargeable and
do the switching in the negative rail so it may look strange at first
glance.

Do you have dry cells installed as well or just the rechargeable? I am
hoping that when switched ON (the switch between terminals 6A and 6B)
you should see the voltage at T8 emitter to ground become a few tens mV
instead as T8 conducts.

I worked a little on Uhers in Munich in the 1970s but always much
preferred Nagras :)

piglet


piglet
 
On Mon, 11 Sep 2023 15:46:02 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 11/09/2023 14:59, Cursitor Doom wrote:
On Mon, 11 Sep 2023 12:57:59 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet

Thanks, Erich. This design seems highly unusual to me and it\'s hard to
work out what\'s going on here. I\'m seeing minus 8V on the emitter of
T8 which makes no sense to me. Es gibt keinen sinn! Does negative 8V
WRT GND seem okay to you??

Yes that circuit does need careful analysis but what you see sounds
correct. T7 and T8 keep dry battery separate from the rechargeable and
do the switching in the negative rail so it may look strange at first
glance.

Do you have dry cells installed as well or just the rechargeable? I am
hoping that when switched ON (the switch between terminals 6A and 6B)
you should see the voltage at T8 emitter to ground become a few tens mV
instead as T8 conducts.

I worked a little on Uhers in Munich in the 1970s but always much
preferred Nagras :)
Click to expand...

Both Uhers and Nagras are becoming highly collectable now for some
reason. There seems to be a renewed interest in tape. A used Uher
Report Monitor in good working order can fetch over 500 euros
currently. For Nagras - jeez - three or four times that price or more!
You\'re obviously way better than I\'ll ever be when it comes to working
out circuit diagrams, Piglet. I\'ll be for ever in your thrawl.
I\'m done today with the tonband but will take another look at it
tomorrow.
Thanks again.
 
On Mon, 11 Sep 2023 15:46:02 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 11/09/2023 14:59, Cursitor Doom wrote:
On Mon, 11 Sep 2023 12:57:59 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet

Thanks, Erich. This design seems highly unusual to me and it\'s hard to
work out what\'s going on here. I\'m seeing minus 8V on the emitter of
T8 which makes no sense to me. Es gibt keinen sinn! Does negative 8V
WRT GND seem okay to you??

Yes that circuit does need careful analysis but what you see sounds
correct. T7 and T8 keep dry battery separate from the rechargeable and
do the switching in the negative rail so it may look strange at first
glance.
Click to expand...

It certainly did look very unusual indeed!

>Do you have dry cells installed as well or just the rechargeable?

There are 3 options at least. You can put 7x D cells in the battery
compartment. You can insert the monolithic NiCad battery into the same
compartment. Or you can insert the PSU (which is the same dimensions
as the NiCad block) into the battery compartment and run it from the
mains supply, and that\'s what I\'ve been doing for testing purposes.
Despite there being power \'in\' to the regulator board, there is
nothing more than 0.7V to be found on any of the component leads. It
should therefore be simple enough to trace the fault, which must
obviously be very close to the \'power in\' point.

I am
hoping that when switched ON (the switch between terminals 6A and 6B)
you should see the voltage at T8 emitter to ground become a few tens mV
instead as T8 conducts.
Click to expand...

Well, I have my doubts, as T8 is a prime suspect here. I\'m very
grateful for your expert advice here, Piglet. What a stroke of luck
you worked for Uher back in the day.

CD.
 
On Mon, 11 Sep 2023 21:29:02 +0100, Cursitor Doom <cd@notformail.com>
wrote:

On Mon, 11 Sep 2023 15:46:02 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 11/09/2023 14:59, Cursitor Doom wrote:
On Mon, 11 Sep 2023 12:57:59 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 10/09/2023 9:29 pm, Cursitor Doom wrote:
Gentlemen,

Can some kind soul tell me what the output voltages of this psu
section are stated as? It\'s not a very good scan I got off the net
and my eyes aren\'t that great any more. In particular I can\'t make out
the polarity. The actual psu is getting 8VDC in from my measurement.
Thanks!


https://disk.yandex.com/i/dmXDbFUsMeZBCg

The regulated output on the left of that pic at TP1 is +4.9V the other
output to the right labelled 6A is the switched battery voltage +5.3 to
+7.8V

piglet

Thanks, Erich. This design seems highly unusual to me and it\'s hard to
work out what\'s going on here. I\'m seeing minus 8V on the emitter of
T8 which makes no sense to me. Es gibt keinen sinn! Does negative 8V
WRT GND seem okay to you??

Yes that circuit does need careful analysis but what you see sounds
correct. T7 and T8 keep dry battery separate from the rechargeable and
do the switching in the negative rail so it may look strange at first
glance.

It certainly did look very unusual indeed!

Do you have dry cells installed as well or just the rechargeable?

There are 3 options at least. You can put 7x D cells in the battery
compartment. You can insert the monolithic NiCad battery into the same
compartment. Or you can insert the PSU (which is the same dimensions
as the NiCad block) into the battery compartment and run it from the
mains supply, and that\'s what I\'ve been doing for testing purposes.
Despite there being power \'in\' to the regulator board, there is
nothing more than 0.7V to be found on any of the component leads. It
should therefore be simple enough to trace the fault, which must
obviously be very close to the \'power in\' point.

I am
hoping that when switched ON (the switch between terminals 6A and 6B)
you should see the voltage at T8 emitter to ground become a few tens mV
instead as T8 conducts.

Well, I have my doubts, as T8 is a prime suspect here. I\'m very
grateful for your expert advice here, Piglet. What a stroke of luck
you worked for Uher back in the day.
Click to expand...

Yup, turned out both T7 and T8 were blown O/C as expected. Strangely
low spec choice of transistor for a position in the circuit like that.
Must have been on the ragged edge a high percentage of the time....
 
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