William Sommerwerck wrote:
wrote in message
...
William Sommerwerck wrote:

I'm guessing that the 7.5V specs are for the lowest voltage
the designers felt gave acceptable performance.

I feel that Grundig assumed the service person would connect
their bench supply between rail ground and "battery +",
not between "battery -" and "battery +".

Unfortunately, they call "power rail voltage" and "battery voltage"
[the same thing. They are different by 2 V in MW mode! ]

aren't the same thing. They are different by 2V in the MW model.

Thanks for fixing that William, but that's not what I
said or meant.

The MW and FM models are the same radio model.

When testing in Medium Wave *mode* the radio
requires 7.5 V between system ground and the power rail and is
specified to draw ca 20 mA. In FM *mode*, the radio is specified
to draw ca 22 mA from that same 7.5 V rail.

This is *not* the same as a 'battery voltage' of 7.5 V.
Our friends at Grundig have the same phrase to describe
'rail voltage' and 'battery voltage', which are normally
ca ~2 V different on the 'return' side.

I now understand that it makes perfect sense to attach our service
supply between 'system ground' and 'power rail' so that the
'system ground' can be bonded to earth ground via the power
supply, for safety. This is not the same as attaching the
supply across the battery, however.

While we're at it... It's perfectly normal for amplifier stages -- tube or
transistor, in any kind of device -- to be fed through a small resistor,
with a largish capacitor to ground.

Yup. In this case, they are decoupling the final audio
stage from the rest of the radio.

This "decouples" the stage from the
power supply, to prevent feedback. The resistor /is not/ present to reduce
the power-supply voltage.

Yet it does, by about 2 V from the battery to power rail.

--Winston

On Mar 12, 10:29*am, Winston wrote:
William Sommerwerck wrote:
*wrote in message
...
William Sommerwerck wrote:

I'm guessing that the 7.5V specs are for the lowest voltage
the designers felt gave acceptable performance.

I feel that Grundig assumed the service person would connect
their bench supply between rail ground and "battery +",
not between "battery -" and "battery +".

Unfortunately, they call "power rail voltage" and "battery voltage"

[the same thing. They are different by 2 V in MW mode! ]

aren't the same thing. They are different by 2V in the MW model.

Thanks for fixing that William, but that's not what I
said or meant.

The MW and FM models are the same radio model.

When testing in Medium Wave *mode* the radio
requires 7.5 V between system ground and the power rail and is
specified to draw ca 20 mA. *In FM *mode*, the radio is specified
to draw ca 22 mA from that same 7.5 V rail.

This is *not* the same as a 'battery voltage' of 7.5 V.
Our friends at Grundig have the same phrase to describe
'rail voltage' and 'battery voltage', which are normally
ca ~2 V different on the 'return' side.

I now understand that it makes perfect sense to attach our service
supply between 'system ground' and 'power rail' so that the
'system ground' can be bonded to earth ground via the power
supply, for safety. *This is not the same as attaching the
supply across the battery, however.

While we're at it... It's perfectly normal for amplifier stages -- tube or
transistor, in any kind of device -- to be fed through a small resistor,
with a largish capacitor to ground.

Yup. *In this case, they are decoupling the final audio
stage from the rest of the radio.

This "decouples" the stage from the
power supply, to prevent feedback. The resistor /is not/ present to reduce
the power-supply voltage.

Yet it does, by about 2 V from the battery to power rail.

--Winston

I was using my RCA Senior Voltohmyst in the beginning. It has either a
10 or 11M impedance, however I built it from a kit I think in 1964. So
being almost 50 years old it's calibration could have been suspect. I
then switched to my Fluke digital. In any case I found that the
readings on both were very close anyway. (I don't use the VTVM much
anymore unless I get an old tube set in here to work on).

My initial reading on R24 before I made any adjustments, with 7.50V
applied to the battery terminals was 1.00V. That voltage rose to
3.60V when C38 would fail. Remember, (after replacing C38) that I
noted an approximate .015 V rise in VR24 when I increased the supply
from 7.50V to 9.0V. Assuming the engineers meant for this voltage to
be set with 9.0V applied, then perhaps I was reading what would be a
perfect bias point (with 7.50V applied), as measured on VR24
initially. It would be nice to know for certain after such an
exercise, but at this point I doubt very much that even someone at
Grundig would be able to shed any further light on this. But then what
you're saying makes perfect sense too Winston. I'm just really
surprised at the ambiguity of the statement on the schematic. In any
event there seems to be an amount of latitude available here, and
given (and I'm assuming) that the radio appears to have been working
that way for many years, perhaps it's a waste of time to fret over .
015V. Maybe I'll set it somewhere in between, enjoy my radio once
again and step back into reality....That would make my wife, who has
failed to see the sense in fixing a 40 year old radio very happy
indeed. Lenny

klem kedidelhopper wrote:
On Mar 12, 10:29 am, wrote:
William Sommerwerck wrote:
wrote in message
...
William Sommerwerck wrote:

I'm guessing that the 7.5V specs are for the lowest voltage
the designers felt gave acceptable performance.

I feel that Grundig assumed the service person would connect
their bench supply between rail ground and "battery +",
not between "battery -" and "battery +".

Unfortunately, they call "power rail voltage" and "battery voltage"

[the same thing. They are different by 2 V in MW mode! ]

aren't the same thing. They are different by 2V in the MW model.

Thanks for fixing that William, but that's not what I
said or meant.

The MW and FM models are the same radio model.

When testing in Medium Wave *mode* the radio
requires 7.5 V between system ground and the power rail and is
specified to draw ca 20 mA. In FM *mode*, the radio is specified
to draw ca 22 mA from that same 7.5 V rail.

This is *not* the same as a 'battery voltage' of 7.5 V.
Our friends at Grundig have the same phrase to describe
'rail voltage' and 'battery voltage', which are normally
ca ~2 V different on the 'return' side.

I now understand that it makes perfect sense to attach our service
supply between 'system ground' and 'power rail' so that the
'system ground' can be bonded to earth ground via the power
supply, for safety. This is not the same as attaching the
supply across the battery, however.

While we're at it... It's perfectly normal for amplifier stages -- tube or
transistor, in any kind of device -- to be fed through a small resistor,
with a largish capacitor to ground.

Yup. In this case, they are decoupling the final audio
stage from the rest of the radio.

This "decouples" the stage from the
power supply, to prevent feedback. The resistor /is not/ present to reduce
the power-supply voltage.

Yet it does, by about 2 V from the battery to power rail.

--Winston

I was using my RCA Senior Voltohmyst in the beginning. It has either a
10 or 11M impedance, however I built it from a kit I think in 1964. So
being almost 50 years old it's calibration could have been suspect. I
then switched to my Fluke digital. In any case I found that the
readings on both were very close anyway. (I don't use the VTVM much
anymore unless I get an old tube set in here to work on).

They were great tools in their day.
I had a PACO and lusted after a Voltohmyst.
http://www.glowbug.nl/valve/Paco-V70.html

My initial reading on R24 before I made any adjustments, with 7.50V
applied to the battery terminals was 1.00V.

Yup. Grundig said "Battery Voltage" but they meant
"Rail Voltage". The two are different. By 2 V!

That voltage rose to
3.60V when C38 would fail. Remember, (after replacing C38) that I
noted an approximate .015 V rise in VR24 when I increased the supply
from 7.50V to 9.0V. Assuming the engineers meant for this voltage to
be set with 9.0V applied, then perhaps I was reading what would be a
perfect bias point (with 7.50V applied), as measured on VR24
initially. It would be nice to know for certain after such an
exercise, but at this point I doubt very much that even someone at
Grundig would be able to shed any further light on this.

I think we have the straight info. I bet the bias when
set with 7.5 V *on the rail* would not drift very much
at all when the radio is powered from a 9 V battery.

But then what
you're saying makes perfect sense too Winston. I'm just really
surprised at the ambiguity of the statement on the schematic.

Someone should write a Grundig Schematic Decoder!

They do present a lot of information but it does take time
to digest the hieroglyphics in order to translate.

In any
event there seems to be an amount of latitude available here, and
given (and I'm assuming) that the radio appears to have been working
that way for many years, perhaps it's a waste of time to fret over .
015V.

I agree. It is probably as close as it needs to be.

Maybe I'll set it somewhere in between, enjoy my radio once
again and step back into reality....That would make my wife, who has
failed to see the sense in fixing a 40 year old radio very happy
indeed.

I agree. There are plenty of 40 year old electronics
to repair everywhere. You should be very pleased to
have your nifty radio back!

--Winston

On Mar 12, 11:59*am, klem kedidelhopper
wrote:
On Mar 12, 10:29*am, Winston wrote:









William Sommerwerck wrote:
*wrote in message
...
William Sommerwerck wrote:

I'm guessing that the 7.5V specs are for the lowest voltage
the designers felt gave acceptable performance.

I feel that Grundig assumed the service person would connect
their bench supply between rail ground and "battery +",
not between "battery -" and "battery +".

Unfortunately, they call "power rail voltage" and "battery voltage"

[the same thing. They are different by 2 V in MW mode! ]

aren't the same thing. They are different by 2V in the MW model.

Thanks for fixing that William, but that's not what I
said or meant.

The MW and FM models are the same radio model.

When testing in Medium Wave *mode* the radio
requires 7.5 V between system ground and the power rail and is
specified to draw ca 20 mA. *In FM *mode*, the radio is specified
to draw ca 22 mA from that same 7.5 V rail.

This is *not* the same as a 'battery voltage' of 7.5 V.
Our friends at Grundig have the same phrase to describe
'rail voltage' and 'battery voltage', which are normally
ca ~2 V different on the 'return' side.

I now understand that it makes perfect sense to attach our service
supply between 'system ground' and 'power rail' so that the
'system ground' can be bonded to earth ground via the power
supply, for safety. *This is not the same as attaching the
supply across the battery, however.

While we're at it... It's perfectly normal for amplifier stages -- tube or
transistor, in any kind of device -- to be fed through a small resistor,
with a largish capacitor to ground.

Yup. *In this case, they are decoupling the final audio
stage from the rest of the radio.

This "decouples" the stage from the
power supply, to prevent feedback. The resistor /is not/ present to reduce
the power-supply voltage.

Yet it does, by about 2 V from the battery to power rail.

--Winston

I was using my RCA Senior Voltohmyst in the beginning. It has either a
10 or 11M impedance, however I built it from a kit I think in 1964. So
being almost 50 years old it's calibration could have been suspect. I
then switched to my Fluke digital. In any case I found that the
readings on both were very close anyway. (I don't use the VTVM much
anymore unless I get an old tube set in here to work on).

My initial reading on R24 before I made any adjustments, with 7.50V
applied to the battery terminals was 1.00V. *That voltage rose to
3.60V when C38 would fail. Remember, (after replacing C38) that I
noted an approximate *.015 V rise in VR24 when I increased the supply
from 7.50V to 9.0V. Assuming the engineers meant for this voltage to
be set with 9.0V applied, then perhaps I was reading what would be a
perfect bias point (with 7.50V applied), as measured on VR24
initially. It would be nice to know for certain after such an
exercise, but at this point I doubt very much that even someone at
Grundig would be able to shed any further light on this. But then what
you're saying makes perfect sense too Winston. I'm just really
surprised at the ambiguity of the statement on the schematic. In any
event there seems to be an amount of latitude available here, and
given (and I'm assuming) that the radio appears to have been working
that way for many years, perhaps it's a waste of time to fret over .
015V. Maybe I'll set it somewhere in between, enjoy my radio once
again and step back into reality....That would make my wife, who has
failed to see the sense in fixing a 40 year old radio very happy
indeed. *Lenny


Well I couldn't resist, so to take this a bit further I checked the
power supply supplied with the radio. It is rated at 9.00V .200A. The
no load voltage is 9.50V. With it connected to the radio and with the
radio playing softly its output drops to 9.25V. In looking at the
schematic again and rereading the statement a few more times I now do
believe that in spite of the ambiguity, the original intention was to
supply 7.50 V to the battery terminals, however reference all
adjustments and voltages to the positive side of C59, (system ground).
So I did that and set the bias on FM to -1.18V. (AF126 I E) I then
recorded the following voltages:

Voltage readings
Test point Radio working:
------------------- --------------------

E. AF178 -1.15V
B. AF178 -1.48V
E. AF124 -1.14V
B. AF124 -1.37V
E. AF121 -0.90V
B. AF121 -1.24V
E. AF126 (1) -1.18V
B. AF126 (1) -1.47V
E. AF126 (II) -1.14V
B. AF126 (II) -1.34V

The voltage across C59 is 6.65V
So now although the radio has been working fine on both AM and FM, I
notice that the first two stages are reading a bit high. I wonder if I
may have another leaky cap. I was looking at possibly C12, C19 and
C32. Assuming I haven't driven everyone nuts with this project yet I
wonder what is the general consensus with this new revelation is?
Lenny

klem kedidelhopper wrote:
On Mar 12, 11:59 am, klem

(...)

Well I couldn't resist, so to take this a bit further I checked the
power supply supplied with the radio. It is rated at 9.00V .200A. The
no load voltage is 9.50V. With it connected to the radio and with the
radio playing softly its output drops to 9.25V. In looking at the
schematic again and rereading the statement a few more times I now do
believe that in spite of the ambiguity, the original intention was to
supply 7.50 V to the battery terminals, however reference all
adjustments and voltages to the positive side of C59, (system ground).
So I did that and set the bias on FM to -1.18V. (AF126 I E) I then
recorded the following voltages:

Here, I added a Vnom column.

Voltage readings
Test point Radio working: Nominal V
------------------- ---------- -----------

E. AF178 -1.15V -0.85
B. AF178 -1.48V -1.15
E. AF124 -1.14V -0.94
B. AF124 -1.37V -1.12
E. AF121 -0.90V -0.85 (MW) -0.60 (FM)
B. AF121 -1.24V -1.05 (MW) -0.95 (FM)
E. AF126 (1) -1.18V -1.18 (MW) -1.15 (FM)
B. AF126 (1) -1.47V -1.45 (MW) -1.4 (FM)
E. AF126 (II) -1.14V -1.05 (MW) -1.0 (FM)
B. AF126 (II) -1.34V -1.33 (MW) -1.0 (FM)

The voltage across C59 is 6.65V

You are testing at Vrail = 6.65 V?

Grundig says "don't bother warming up the VTVM unless
Vrail ==7.5 V" ( I heard them. Really I did.

So now although the radio has been working fine on both AM and FM, I
notice that the first two stages are reading a bit high. I wonder if I
may have another leaky cap. I was looking at possibly C12, C19 and
C32.

The little 'K' symbol next to these three apparently
denotes a ceramic cap. These 500 V units could become
extremely leaky at 2 V I suppose.

I wouldn't bet that way, however.


There are lots more things that need your attention more
than your beloved radio. Personally, I think that at this
rate, in another 30 days, you will become borderline
obsessive.

My advice: Button it up and listen to it while doing one or mo

Clean or replace the sacrificial anode in your water heater

Do an oil change on your car

Flush and fill your car radiator

Rotate your tires

Replace the transmission fluid in your car
(Clean your funnel and flush with clean ATF first!)

Grab a basket and fill it with stuff from the back seat
and trunk. Neatly put away, toss or donate the contents
of the basket.

Shampoo car carpets

Diagnose that rattle in your clothes dryer

Vacuum out your dryer exhaust vent

Clean your gutters

Replace clogged rafter end vents with new ones

Replace the nasty 'wiring' job in the garage with
real Romex or conduit as code permits.

Install a chimney - mount 'Over The Air' antenna and cancel
your cable TV subscription

Scavenge stuff out of one room or garage that you
honestly will never need and give it to your local
Freecycler

Buy a little microcontroller board and teach yourself
assembly language. Make a robot.

etc. etc.


--Winston

On Mar 12, 5:17*pm, Winston wrote:
klem kedidelhopper wrote:
On Mar 12, 11:59 am, klem

(...)

Well I couldn't resist, so to take this a bit further I checked the
power supply supplied with the radio. It is rated at 9.00V .200A. The
no load voltage is 9.50V. With it connected to the radio and with the
radio playing softly its output drops to 9.25V. In looking at the
schematic again and rereading the statement a few more times I now do
believe that in spite of the ambiguity, the original intention was to
supply 7.50 V to *the battery terminals, however reference all
adjustments and voltages to the positive side of C59, (system ground).
So I did that and set the bias on FM to -1.18V. (AF126 I E) I then
recorded the following voltages:

Here, I added a Vnom column.









* * * * * * * Voltage readings
* * Test point * * * * * Radio working: * *Nominal V
------------------- * * * * ---------- * * -----------

* * E. AF178 * * * * * * * *-1.15V * * * * * * * * -0.85
* * B. AF178 * * * * * * * *-1.48V * * * * -1.15
* * E. AF124 * * * * * * * *-1.14V * * * * -0.94
* * B. AF124 * * * * * * * *-1.37V * * * * -1.12
* * E. AF121 * * * * * * * *-0.90V * * * * -0.85 (MW) -0.60 (FM)
* * B. AF121 * * * * * * * *-1.24V * * * * -1.05 (MW) -0.95 (FM)
* * E. AF126 (1) * * * * * -1.18V * * * * *-1.18 (MW) -1.15 (FM)
* * B. AF126 (1) * * * * * -1.47V * * * * *-1.45 (MW) -1.4 (FM)
* * E. AF126 (II) * * * * * -1.14V * * * * -1.05 (MW) -1.0 (FM)
* * B. AF126 (II) * * * * * -1.34V * * * * -1.33 (MW) -1.0 (FM)

The *voltage across C59 is 6.65V

You are testing at Vrail = 6.65 V?

Grundig says "don't bother warming up the VTVM unless
Vrail ==7.5 V" *( I heard them. *Really I did. *

So now although the radio has been working fine on both AM and FM, I
notice that the first two stages are reading a bit high. I wonder if I
may have another leaky cap. I was looking at possibly C12, C19 and
C32.

The little 'K' symbol next to these three apparently
denotes a ceramic cap. These 500 V units could become
extremely leaky at 2 V I suppose.

I wouldn't bet that way, however.

There are lots more things that need your attention more
than your beloved radio. *Personally, I think that at this
rate, in another 30 days, you will become borderline
obsessive. *

My advice: Button it up and listen to it while doing one or mo

* * * * Clean or replace the sacrificial anode in your water heater

* * * * Do an oil change on your car

* * * * Flush and fill your car radiator

* * * * Rotate your tires

* * * * Replace the transmission fluid in your car
* * * * (Clean your funnel and flush with clean ATF first!)

* * * * Grab a basket and fill it with stuff from the back seat
* * * * and trunk. *Neatly put away, toss or donate the contents
* * * * of the basket.

* * * * Shampoo car carpets

* * * * Diagnose that rattle in your clothes dryer

* * * * Vacuum out your dryer exhaust vent

* * * * Clean your gutters

* * * * Replace clogged rafter end vents with new ones

* * * * Replace the nasty 'wiring' job in the garage with
* * * * real Romex or conduit as code permits.

* * * * Install a chimney - mount 'Over The Air' antenna and cancel
* * * * your cable TV subscription

* * * * Scavenge stuff out of one room or garage that you
* * * * honestly will never need and give it to your local
* * * * Freecycler

* * * * Buy a little microcontroller board and teach yourself
* * * * assembly language. *Make a robot.

* * * * etc. etc. *

--Winston

Wow! I'll never complain about my wife nagging me again. I think
you've covered everything. Lenny

klem kedidelhopper wrote:

(...)

Wow! I'll never complain about my wife nagging me again. I think
you've covered everything. Lenny



--Winston--Nag, whine, nag, nag, nag.

On Mar 12, 8:19*pm, Winston wrote:
klem kedidelhopper wrote:

(...)

Wow! I'll never complain about my wife nagging me again. *I think
you've covered everything. Lenny



--Winston--Nag, whine, nag, nag, nag.

I never thought of myself as being obsessive compulsive. In fact I've
been contemplating that for months and have finally decided that I'm
not...

I put the radio together last night. I'm listening to it right now.
It's nice to be able to "see" my bench again, and be done with this
project. It seems to play fine on both bands, in spite of the slight
difference in readings on the front end. I'm not going to worry about
that or the exact bias point for that matter. I have all my notes and
that's a project for another day, (maybe). I'm grateful that it's
working, and so well, and for all the friends who've helped me along
the way.

You'll have to excuse me now though. I have to go build a garage, so
that I can clean it out. Thanks again to everyone.
Best regards, Lenny

PS. I'll let you know when the next Philco Predicta walks in here...