Re: SM-220 scope question
I replaced all the oil/paper capacitors with metallised polypropylene, but that didn't fix the problem.
?
Then I realised that it only occurred on the higher sweep ranges, so I looked at the blanking pulse and horizontal deflection.
?
Here they are on the 100-1k range:
?
?
That looks OK so I repeated the measurement on the 10-100k range:
?
?
Aha! The blanking pulse amplitude is 10 volts lower and it doesn't align with the initial part of the flyback.
?
Now I need to find out which components are causing it.
?
--
Mike G8GYW
|
|
|
Re: TS50 high current draw
I found the problem, Q5. It was causing all the high current draw.
Now the million dollar question, where to get a replacement(s). Looking at Mouser, the MRF421 may be a replacement.?
I'll be researching?
Bob W4JFA?
Lou, I found it and joined. It looks like the posts need to be approved B4 they go out. Thanks for calling that to my attention. Bob W4JFA?
I didn't know there was one. I'll look now. Thank you. Bob W4JFA?
Have you tried the TS-50 Group?
Lou WA5LOU
I have enuff test equipment. I only lack good unsoldering equipment. What I have has been fine 99%?of the time but I just can't? get this transistor unsoldered. I'm pretty close to believing that the transistor leaks under the full 14 volts but does not leak under the? DVOM diode test. That's why I tried to unsolder the collector and test cuzz that would have answered my?questions.?
I do like to ask on groups?like this cuzz you never know who may have had the same issue at one time.
Thanks for your help. I'll let you know.
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via
wrote:
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
Lou, I found it and joined. It looks like the posts need to be approved B4 they go out. Thanks for calling that to my attention. Bob W4JFA?
I didn't know there was one. I'll look now. Thank you. Bob W4JFA?
Have you tried the TS-50 Group?
Lou WA5LOU
I have enuff test equipment. I only lack good unsoldering equipment. What I have has been fine 99%?of the time but I just can't? get this transistor unsoldered. I'm pretty close to believing that the transistor leaks under the full 14 volts but does not leak under the? DVOM diode test. That's why I tried to unsolder the collector and test cuzz that would have answered my?questions.?
I do like to ask on groups?like this cuzz you never know who may have had the same issue at one time.
Thanks for your help. I'll let you know.
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via
wrote:
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
I didn't know there was one. I'll look now. Thank you. Bob W4JFA?
Have you tried the TS-50 Group?
Lou WA5LOU
I have enuff test equipment. I only lack good unsoldering equipment. What I have has been fine 99%?of the time but I just can't? get this transistor unsoldered. I'm pretty close to believing that the transistor leaks under the full 14 volts but does not leak under the? DVOM diode test. That's why I tried to unsolder the collector and test cuzz that would have answered my?questions.?
I do like to ask on groups?like this cuzz you never know who may have had the same issue at one time.
Thanks for your help. I'll let you know.
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via
wrote:
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
Have you tried the TS-50 Group?
Lou WA5LOU
I have enuff test equipment. I only lack good unsoldering equipment. What I have has been fine 99%?of the time but I just can't? get this transistor unsoldered. I'm pretty close to believing that the transistor leaks under the full 14 volts but does not leak under the? DVOM diode test. That's why I tried to unsolder the collector and test cuzz that would have answered my?questions.?
I do like to ask on groups?like this cuzz you never know who may have had the same issue at one time.
Thanks for your help. I'll let you know.
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via
wrote:
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
I have enuff test equipment. I only lack good unsoldering equipment. What I have has been fine 99%?of the time but I just can't? get this transistor unsoldered. I'm pretty close to believing that the transistor leaks under the full 14 volts but does not leak under the? DVOM diode test. That's why I tried to unsolder the collector and test cuzz that would have answered my?questions.?
I do like to ask on groups?like this cuzz you never know who may have had the same issue at one time.
Thanks for your help. I'll let you know.
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via
wrote:
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
The transistor needs to be completely removed to properly test
it. If it's still good, start testing everything around it. Keep
in mind that if you don't have adequate test equipment (and
knowledge), you can do a lot more damage trying to do it yourself.
Gary
On 5/29/2025 7:43 PM, Bob via groups.io
wrote:
toggle quoted message
Show quoted text
Oh I have, with the finger, it's Q6. I tried to get
the collector unsoldered so I could test but I can't get it
unsoldered. I have the electric solenoid
desoldering tool, I have solder braid, and the manual
"clicker" type solder sucker but I can't get it off. I may
have to find someone locally that
can unsolder that for me. My thoughts were if I
remove only the collector and the current draw disappears, I
found it.
Bob W4JFA
?
If you have a thermal camera, now's the time to use it.
If not, start using your finger to find the overheating
device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via wrote:
Start checking diodes, resistors and capacitors until
you find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could
use some advice.
The radio had no RF out. Was narrowed down to
the final board.
It then started blowing fuses. It's not now and
I don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit,
they test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
Oh I have, with the finger, it's Q6. I tried to get the collector unsoldered so I could test but I can't get it unsoldered. I have the electric solenoid desoldering tool, I have solder braid, and the manual "clicker" type solder sucker but I can't get it off. I may have to find someone locally that can unsolder that for me. My thoughts were if I remove only the collector and the current draw disappears, I found it. Bob W4JFA
?
If you have a thermal camera, now's the time to use it. If not,
start using your finger to find the overheating device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via
wrote:
Start checking diodes, resistors and capacitors until you find
it.
Gary
On 5/29/2025 6:56 PM, Bob via
wrote:
Hi all,
If anyone is familiar with the TS-50, I could use some
advice.
The radio had no RF out. Was narrowed down to the final
board.
It then started blowing fuses. It's not now and I don't
know why however
it does draw 6 amps on receive and also draws 6 amps
with the power off.
Checking the final transistors, in circuit, they test
OK with a DVOM on diode
test. I read no shorts from collector to base/ground.
Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm missing
something?obvious?
If anyone has any hints I sure would appreciate it.
73, Bob W4JFA
|
Re: TS50 high current draw
It could be shorted, or another device may have opened, and
current is taking an alternative route through the transistor.
Remove the transistor, then apply power again.
Gary
On 5/29/2025 7:15 PM, Bob via groups.io
wrote:
toggle quoted message
Show quoted text
I've obviously missing something because I've
checked everything I can and am not finding a bad part. Another
symptom is the final transistors
especially Q6, gets hot. My guess the excessive current
draw is related to this. Looking at the schematic, there's 12
volts going to the collector
all the?time. Since the transistor?gets hot, that tells me
the current is going through the transistor from the collector
to the base which is grounded
through resistors and the emitters are directly grounded.
Do you think the transistor(s) are leaking under the power
supply 14 volts but not leaking with the small current?the
DVOM puts out on the diode test?
Thank you.
Bob W4JFA
Start checking diodes, resistors and capacitors until you
find it.
Gary
On 5/29/2025 6:56 PM, Bob via wrote:
Hi all,
If anyone is familiar with the TS-50, I could use
some advice.
The radio had no RF out. Was narrowed down to the
final board.
It then started blowing fuses. It's not now and I
don't know why however
it does draw 6 amps on receive and also draws 6
amps with the power off.
Checking the final transistors, in circuit, they
test OK with a DVOM on diode
test. I read no shorts from collector to
base/ground. Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm
missing something?obvious?
If anyone has any hints I sure would appreciate
it.
73, Bob W4JFA
|
Re: TS50 high current draw
I've obviously missing something because I've checked everything I can and am not finding a bad part. Another symptom is the final transistors especially Q6, gets hot. My guess the excessive current draw is related to this. Looking at the schematic, there's 12 volts going to the collector all the?time. Since the transistor?gets hot, that tells me the current is going through the transistor from the collector to the base which is grounded through resistors and the emitters are directly grounded.
Do you think the transistor(s) are leaking under the power supply 14 volts but not leaking with the small current?the DVOM puts out on the diode test?
Thank you.
Bob W4JFA
Start checking diodes, resistors and capacitors until you find
it.
Gary
On 5/29/2025 6:56 PM, Bob via
wrote:
Hi all,
If anyone is familiar with the TS-50, I could use some
advice.
The radio had no RF out. Was narrowed down to the final
board.
It then started blowing fuses. It's not now and I don't
know why however
it does draw 6 amps on receive and also draws 6 amps with
the power off.
Checking the final transistors, in circuit, they test OK
with a DVOM on diode
test. I read no shorts from collector to base/ground.
Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm missing
something?obvious?
If anyone has any hints I sure would appreciate it.
73, Bob W4JFA
|
Re: TS50 high current draw
If you have a thermal camera, now's the time to use it. If not,
start using your finger to find the overheating device.
Gary
On 5/29/2025 7:01 PM, Gary Cook via
groups.io wrote:
toggle quoted message
Show quoted text
Start checking diodes, resistors and capacitors until you find
it.
Gary
On 5/29/2025 6:56 PM, Bob via
groups.io wrote:
Hi all,
If anyone is familiar with the TS-50, I could use some
advice.
The radio had no RF out. Was narrowed down to the final
board.
It then started blowing fuses. It's not now and I don't
know why however
it does draw 6 amps on receive and also draws 6 amps
with the power off.
Checking the final transistors, in circuit, they test
OK with a DVOM on diode
test. I read no shorts from collector to base/ground.
Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm missing
something?obvious?
If anyone has any hints I sure would appreciate it.
73, Bob W4JFA
|
Re: TS50 high current draw
Start checking diodes, resistors and capacitors until you find
it.
Gary
On 5/29/2025 6:56 PM, Bob via groups.io
wrote:
toggle quoted message
Show quoted text
Hi all,
If anyone is familiar with the TS-50, I could use some
advice.
The radio had no RF out. Was narrowed down to the final
board.
It then started blowing fuses. It's not now and I don't
know why however
it does draw 6 amps on receive and also draws 6 amps with
the power off.
Checking the final transistors, in circuit, they test OK
with a DVOM on diode
test. I read no shorts from collector to base/ground.
Reverse polarity diode
tests good.
This should be a simple diagnosis so maybe I'm missing
something?obvious?
If anyone has any hints I sure would appreciate it.
73, Bob W4JFA
|
Hi all, If anyone is familiar with the TS-50, I could use some advice.
The radio had no RF out. Was narrowed down to the final board. It then started blowing fuses. It's not now and I don't know why however it does draw 6 amps on receive and also draws 6 amps with the power off.
Checking the final transistors, in circuit, they test OK with a DVOM on diode test. I read no shorts from collector to base/ground. Reverse polarity diode tests good.
This should be a simple diagnosis so maybe I'm missing something?obvious?
If anyone has any hints I sure would appreciate it.
73, Bob W4JFA
|
Re: SM-220 scope question
I found time to have a quick look at the waveforms.
?
Here is the output of the blanking pulse generator going into C135:
?
?
This is the other side of C135 where it connects to the CRT cathode:
?
?
Perhaps the capacitor is dead?
?
--
Mike G8GYW
|
Re: SM-220 scope question
Of course, but it will be a couple of weeks as I have a holiday coming up.
?
--
Mike G8GYW
|
Re: SM-220 scope question
Let us know how you do. Bob W4JFA?
I found the service manual which clearly states that the flyback should be blanked.
?
The circuit that creates the blanking pulse is just two transistors and a capacitor so it shouldn't be hard to fix.
?
--
Mike G8GYW
|
Re: SM-220 scope question
I found the service manual which clearly states that the flyback should be blanked.
?
The circuit that creates the blanking pulse is just two transistors and a capacitor so it shouldn't be hard to fix.
?
--
Mike G8GYW
|
I noticed recently that in oscilloscope mode the flyback is partially visible. Is this a feature or a fault, and if it's a fault can it be fixed?
?
?
--
Mike G8GYW
|
Re: TM-V71E LEFT HAND RADIO FAULT
Repeating the cable didn't help
?
Kind regards,
Mike?
G3ZCC
|
Bob
Lou WA5LOU
Mike Davidsohn G3ZCC