I set the dead key on AM to one watt and when the radio gets hot, it goes
back up to almost full wattage and modulation sounds "pinchy" according to
reports. I have to then cool it off before it will act normal again. Does
anyone else see this with theirs? Mine is in my vehicle so the temperatures
do get extreme. I find this happens a lot after it's been parked in the sun
for a while. Today I tested my temperature theory by taking the cover off
and holding the radio in front of the ac vent so it would cool off fast. It
went back to normal in just under a minute. Sounds like a weak regulator. I
hope some one has seen this before and knows the solution. I don't have a
schematic for it. :-(

tia,
Dr.X

On Wed, 18 Aug 2004 21:10:10 -0400, "Dr.X" wrote
in :

I set the dead key on AM to one watt and when the radio gets hot, it goes
back up to almost full wattage and modulation sounds "pinchy" according to
reports. I have to then cool it off before it will act normal again. Does
anyone else see this with theirs? Mine is in my vehicle so the temperatures
do get extreme. I find this happens a lot after it's been parked in the sun
for a while. Today I tested my temperature theory by taking the cover off
and holding the radio in front of the ac vent so it would cool off fast. It
went back to normal in just under a minute. Sounds like a weak regulator. I
hope some one has seen this before and knows the solution. I don't have a
schematic for it. :-(

tia,
Dr.X


What you are experiencing is called "thermal runaway" and is most
likely caused by either high quiescient collector current or a failure
of the heatsink coupling (loose power transistor). You need to take it
to a competent tech.






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"Frank Gilliland" wrote in message
...
On Wed, 18 Aug 2004 21:10:10 -0400, "Dr.X" wrote
in :

I set the dead key on AM to one watt and when the radio gets hot, it goes
back up to almost full wattage and modulation sounds "pinchy" according
to
reports. I have to then cool it off before it will act normal again. Does
anyone else see this with theirs? Mine is in my vehicle so the
temperatures
do get extreme. I find this happens a lot after it's been parked in the
sun
for a while. Today I tested my temperature theory by taking the cover off
and holding the radio in front of the ac vent so it would cool off fast.
It
went back to normal in just under a minute. Sounds like a weak regulator.
I
hope some one has seen this before and knows the solution. I don't have a
schematic for it. :-(

tia,
Dr.X


What you are experiencing is called "thermal runaway" and is most
likely caused by either high quiescient collector current or a failure
of the heatsink coupling (loose power transistor). You need to take it
to a competent tech.

Hi Frank. Thanks for answering.

I thought it was thermal runaway also, but I don't think so now. Although
the results are the same. Thermal runaway happens when the component
generates enough of its own heat to send it on its way. The issue I'm having
starts at 160 degrees F. The interior of the van gets to 168 sitting in the
Florida sun. Transmitting a dead key at 10 watts with an swr of 2:1 only
gets me 91 F and never goes into runaway. The heat sink compound is doing
it's job as is the sink itself. The final rf area never even gets warm.

The only hot spot in the radio is what appears to be a regulator mounted at
the left side about 2 in. behind the mode selection switch. I can't say what
that does since I don't have a schematic and I really haven't started poking
around in this radio yet (other than a quick crystal swap).

As for having a competent tech look at it, well I've been a component level
technician for about 20 years but haven't messed with radio in about 10
years. A competent tech with a 10 year gap would want a schematic. ;-)

Thanks again for the reply.
-Dr.X

On Wed, 18 Aug 2004 23:12:09 -0400, "Dr.X" wrote
in :

"Frank Gilliland" wrote in message
.. .
On Wed, 18 Aug 2004 21:10:10 -0400, "Dr.X" wrote
in :

I set the dead key on AM to one watt and when the radio gets hot, it goes
back up to almost full wattage and modulation sounds "pinchy" according
to
reports. I have to then cool it off before it will act normal again. Does
anyone else see this with theirs? Mine is in my vehicle so the
temperatures
do get extreme. I find this happens a lot after it's been parked in the
sun
for a while. Today I tested my temperature theory by taking the cover off
and holding the radio in front of the ac vent so it would cool off fast.
It
went back to normal in just under a minute. Sounds like a weak regulator.
I
hope some one has seen this before and knows the solution. I don't have a
schematic for it. :-(

tia,
Dr.X


What you are experiencing is called "thermal runaway" and is most
likely caused by either high quiescient collector current or a failure
of the heatsink coupling (loose power transistor). You need to take it
to a competent tech.

Hi Frank. Thanks for answering.

I thought it was thermal runaway also, but I don't think so now. Although
the results are the same. Thermal runaway happens when the component
generates enough of its own heat to send it on its way. The issue I'm having
starts at 160 degrees F. The interior of the van gets to 168 sitting in the
Florida sun. Transmitting a dead key at 10 watts with an swr of 2:1 only
gets me 91 F and never goes into runaway. The heat sink compound is doing
it's job as is the sink itself. The final rf area never even gets warm.

The only hot spot in the radio is what appears to be a regulator mounted at
the left side about 2 in. behind the mode selection switch. I can't say what
that does since I don't have a schematic and I really haven't started poking
around in this radio yet (other than a quick crystal swap).

As for having a competent tech look at it, well I've been a component level
technician for about 20 years but haven't messed with radio in about 10
years. A competent tech with a 10 year gap would want a schematic. ;-)


Then what you are asking for is a schematic. Sorry, I don't have one
for your radio.





-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
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"Frank Gilliland" wrote in message
...
On Wed, 18 Aug 2004 23:12:09 -0400, "Dr.X" wrote
in :

"Frank Gilliland" wrote in message
.. .
On Wed, 18 Aug 2004 21:10:10 -0400, "Dr.X" wrote
in :

I set the dead key on AM to one watt and when the radio gets hot, it
goes
back up to almost full wattage and modulation sounds "pinchy"
according
to
reports. I have to then cool it off before it will act normal again.
Does
anyone else see this with theirs? Mine is in my vehicle so the
temperatures
do get extreme. I find this happens a lot after it's been parked in
the
sun
for a while. Today I tested my temperature theory by taking the cover
off
and holding the radio in front of the ac vent so it would cool off
fast.
It
went back to normal in just under a minute. Sounds like a weak
regulator.
I
hope some one has seen this before and knows the solution. I don't
have a
schematic for it. :-(

tia,
Dr.X


What you are experiencing is called "thermal runaway" and is most
likely caused by either high quiescient collector current or a failure
of the heatsink coupling (loose power transistor). You need to take it
to a competent tech.

Hi Frank. Thanks for answering.

I thought it was thermal runaway also, but I don't think so now. Although
the results are the same. Thermal runaway happens when the component
generates enough of its own heat to send it on its way. The issue I'm
having
starts at 160 degrees F. The interior of the van gets to 168 sitting in
the
Florida sun. Transmitting a dead key at 10 watts with an swr of 2:1 only
gets me 91 F and never goes into runaway. The heat sink compound is doing
it's job as is the sink itself. The final rf area never even gets warm.

The only hot spot in the radio is what appears to be a regulator mounted
at
the left side about 2 in. behind the mode selection switch. I can't say
what
that does since I don't have a schematic and I really haven't started
poking
around in this radio yet (other than a quick crystal swap).

As for having a competent tech look at it, well I've been a component
level
technician for about 20 years but haven't messed with radio in about 10
years. A competent tech with a 10 year gap would want a schematic. ;-)


Then what you are asking for is a schematic. Sorry, I don't have one
for your radio.

Yes, I guess I am asking for a schematic. But I was also hoping that some
one had already experienced this and would save me some time. That's ok,
I'll just keep looking for a schematic or just use some common sense to
track it down. I'll be getting into it this weekend anyway to tinker around.
I'll fix it then.

Thanks again Frank.
-Dr.X

Dr.X wrote:
"Frank Gilliland" wrote in message
...

On Wed, 18 Aug 2004 23:12:09 -0400, "Dr.X" wrote
in :


"Frank Gilliland" wrote in message
...

On Wed, 18 Aug 2004 21:10:10 -0400, "Dr.X" wrote
in :


I set the dead key on AM to one watt and when the radio gets hot, it

goes

back up to almost full wattage and modulation sounds "pinchy"

according

to

reports. I have to then cool it off before it will act normal again.

Does

anyone else see this with theirs? Mine is in my vehicle so the

temperatures

do get extreme. I find this happens a lot after it's been parked in

the

sun

for a while. Today I tested my temperature theory by taking the cover

off

and holding the radio in front of the ac vent so it would cool off

fast.

It

went back to normal in just under a minute. Sounds like a weak

regulator.

I

hope some one has seen this before and knows the solution. I don't

have a

schematic for it. :-(

tia,
Dr.X


What you are experiencing is called "thermal runaway" and is most
likely caused by either high quiescient collector current or a failure
of the heatsink coupling (loose power transistor). You need to take it
to a competent tech.

Hi Frank. Thanks for answering.

I thought it was thermal runaway also, but I don't think so now. Although
the results are the same. Thermal runaway happens when the component
generates enough of its own heat to send it on its way. The issue I'm

having

starts at 160 degrees F. The interior of the van gets to 168 sitting in

the

Florida sun. Transmitting a dead key at 10 watts with an swr of 2:1 only
gets me 91 F and never goes into runaway. The heat sink compound is doing
it's job as is the sink itself. The final rf area never even gets warm.

The only hot spot in the radio is what appears to be a regulator mounted

at

the left side about 2 in. behind the mode selection switch. I can't say

what

that does since I don't have a schematic and I really haven't started

poking

around in this radio yet (other than a quick crystal swap).

As for having a competent tech look at it, well I've been a component

level

technician for about 20 years but haven't messed with radio in about 10
years. A competent tech with a 10 year gap would want a schematic. ;-)


Then what you are asking for is a schematic. Sorry, I don't have one
for your radio.


Yes, I guess I am asking for a schematic. But I was also hoping that some
one had already experienced this and would save me some time. That's ok,
I'll just keep looking for a schematic or just use some common sense to
track it down. I'll be getting into it this weekend anyway to tinker around.
I'll fix it then.

Thanks again Frank.
-Dr.X


Hello,
I think I can help a bit.
I have a schematic available online at:
http://rogerbird.tripod.com/diagrams/
(its an unlinked page on my site - Shhh)
Ic 6 is the 8v regulator you are talking about.
One of the common causes of regulator problems in the HR series radios
is the fact that many of the Electrolytics are only 10v. These have been
known to cause issues on the 8V supply line and in the audio sections.
You may want to hit a couple with some freeze spray or just see if they
are getting hot.
Check C52 & C33 (47uf 10v) C60(470uf 10v).
In the audio Ckt C95 (470uf 10v) and C97 (47uf 10v).
I usually replace these with the same value just Higher voltage (16 to
25v) caps. There are others that can cause problems, but with your
issue I would start there.

Also I would check the Bias diodes on the driver and final. They could
cause the problem you are having. (d77 and D78 - MV1YHS).

I hope this helps,

Rogerbird

"Rogerbird1" wrote in message ...
....

Hello,
I think I can help a bit.
I have a schematic available online at:
http://rogerbird.tripod.com/diagrams/
(its an unlinked page on my site - Shhh)
Ic 6 is the 8v regulator you are talking about.
One of the common causes of regulator problems in the HR series radios
is the fact that many of the Electrolytics are only 10v. These have been
known to cause issues on the 8V supply line and in the audio sections.
You may want to hit a couple with some freeze spray or just see if they
are getting hot.
Check C52 & C33 (47uf 10v) C60(470uf 10v).
In the audio Ckt C95 (470uf 10v) and C97 (47uf 10v).
I usually replace these with the same value just Higher voltage (16 to
25v) caps. There are others that can cause problems, but with your
issue I would start there.

Also I would check the Bias diodes on the driver and final. They could
cause the problem you are having. (d77 and D78 - MV1YHS).

I hope this helps,

Rogerbird

Hi Rogerbird.

Thanks for the help. I will definitely check those caps out this weekend. I
have downloaded the files you referred to. Thank you VERY much. I really
appreciate your taking the time.

Dr.X (glad there are Rogerbirds out there)

I don't know that I'd be overly concerned with caps unless they are in the
regulator circuit that supplies dc voltage to the final.
I suspect that the regulator/modulator pass transistor is breaking down when
heated, or something in that circuit.
If it were the bias regulator diodes, the power wouldn't rise that much.



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"Dr.X" wrote in message
...
"Rogerbird1" wrote in message ...
...

Hello,
I think I can help a bit.
I have a schematic available online at:
http://rogerbird.tripod.com/diagrams/
(its an unlinked page on my site - Shhh)
Ic 6 is the 8v regulator you are talking about.
One of the common causes of regulator problems in the HR series radios
is the fact that many of the Electrolytics are only 10v. These have been
known to cause issues on the 8V supply line and in the audio sections.
You may want to hit a couple with some freeze spray or just see if they
are getting hot.
Check C52 & C33 (47uf 10v) C60(470uf 10v).
In the audio Ckt C95 (470uf 10v) and C97 (47uf 10v).
I usually replace these with the same value just Higher voltage (16 to
25v) caps. There are others that can cause problems, but with your
issue I would start there.

Also I would check the Bias diodes on the driver and final. They could
cause the problem you are having. (d77 and D78 - MV1YHS).

I hope this helps,

Rogerbird

Hi Rogerbird.

Thanks for the help. I will definitely check those caps out this weekend.
I
have downloaded the files you referred to. Thank you VERY much. I really
appreciate your taking the time.

Dr.X (glad there are Rogerbirds out there)


Not sure you really have a problem. Mine did this on a trip to Florida too
after setting in Disney World parking lot all day. Never had this problem
again.Think it is just too hot. Probably shouldnt be operating the radio at
that temp anyway.

"Jimmie" wrote in message
r.com...
....
Not sure you really have a problem. Mine did this on a trip to Florida too
after setting in Disney World parking lot all day. Never had this problem
again.Think it is just too hot. Probably shouldnt be operating the radio
at
that temp anyway.

Maybe I should consider running an air conditioner duct to the radio. :-]

-Dr.X