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Hi everyone
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I bought this radio from a dealer a year ago. It is in immaculate condition despite its age and worked flawlessly until now.
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It would start to drop out of TX occasionally during a QSO and I initially suspected my PTT switch.
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Now it won't transmit at all. I have tried PTT on the front panel mic connector, the rear ACC2 socket, the SEND button and AT TUNE.
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Any ideas where I should start looking for the fault?
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Mike G8GYW
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Possible that the ALC board DC-DC converter has quit. I had that happen to my TS850; all the lights but no TX. Just my guess.
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On Wed, Mar 12, 2025 at 12:34 PM, David Frechette wrote:
Possible that the ALC board DC-DC converter has quit. I had that happen to my TS850; all the lights but no TX. Just my guess.
Thank you David. My plan is to (hopefully) gather some suggestions before opening it up.
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Mike G8GYW
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You should be able to find a schematic and trace the circuit, at least in theory!
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On Wed, Mar 12, 2025 at 03:12 PM, David Frechette wrote:
You should be able to find a schematic and trace the circuit, at least in theory!
I have the schematic, just hoping for some pointers. Nothing happens when I operate PTT, it stays in RX.
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Mike G8GYW
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If you haven't already, try a factory full reset. I'm not a professional tech but I've fixed 2 radios in the past year and a half doing a full reset. Bob W4JFA?
On Wed, Mar 12, 2025 at 03:12 PM, David Frechette wrote:
You should be able to find a schematic and trace the circuit, at least in theory!
I have the schematic, just hoping for some pointers. Nothing happens when I operate PTT, it stays in RX.
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Mike G8GYW
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On Wed, Mar 12, 2025 at 04:39 PM, Bob wrote:
If you haven't already, try a factory full reset. I'm not a professional tech but I've fixed 2 radios in the past year and a half doing a full reset.
Bob W4JFA
Thanks Bob. I tried the Full Reset described in the instruction manual ([A=B] + POWER ON) to no effect.
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Is that the same as the factory reset?
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The Mic socket and ACC2 are wired to the TX-RX Unit X57-4620-00. Unfortunately the schematic in my downloaded copy of the service manual is very fuzzy. Is there a better one somewhere?
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Mike G8GYW
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Get the service manual and read the portion that
deals with the RX/TX change-over. I'm pretty sure you'll find a description as
to how the change-over is implemented. Normally there are voltages such as RXB
and TXB or similar, which are switched on the transition.
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Clearly that process is not working since RX
doesn't turn off when you try to transmit...That's likely your first
clue...
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I hope this helps....73...Jordan VE6ZT
----- Original Message -----
Sent: Wednesday, March 12, 2025 9:51
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
On Wed, Mar 12, 2025 at 03:12 PM, David Frechette wrote:
You should be able to find a schematic and trace the circuit, at
least in theory!
I have the schematic, just hoping for some pointers. Nothing happens when
I operate PTT, it stays in RX.
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--
Mike G8GYW
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Manuals sometimes show a partial reset and a full or complete reset. Bob W4JFA
On Wed, Mar 12, 2025 at 04:39 PM, Bob wrote:
If you haven't already, try a factory full reset. I'm not a professional tech but I've fixed 2 radios in the past year and a half doing a full reset.
Bob W4JFA
Thanks Bob. I tried the Full Reset described in the instruction manual ([A=B] + POWER ON) to no effect.
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Is that the same as the factory reset?
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The Mic socket and ACC2 are wired to the TX-RX Unit X57-4620-00. Unfortunately the schematic in my downloaded copy of the service manual is very fuzzy. Is there a better one somewhere?
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Mike G8GYW
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What is that scorched discolored area...??
Looks like something arced or burned...
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Jordan...
----- Original Message -----
Sent: Thursday, March 13, 2025 6:15
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
Manuals sometimes show a partial reset and a full or complete
reset.
Bob W4JFA
On Wed, Mar 12, 2025 at 04:39 PM, Bob wrote:
If you haven't already, try a factory full reset. I'm not a
professional tech but I've fixed 2 radios in the past year and a half
doing a full reset.
Bob W4JFA
Thanks Bob. I tried the Full Reset described in the instruction manual
([A=B] + POWER ON) to no effect.
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Is that the same as the factory reset?
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The Mic socket and ACC2 are wired to the TX-RX Unit X57-4620-00.
Unfortunately the schematic in my downloaded copy of the service manual is
very fuzzy. Is there a better one somewhere?
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Mike G8GYW
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Thanks Jordan, yes that was helpful.
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I found a good quality set of schematics on mods.dk and have identified the TX/RX relay which is switched by a TXB line.
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Time to start probing ...
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Mike G8GYW
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On Thu, Mar 13, 2025 at 12:44 PM, Jordan wrote:
What is that scorched discolored area...?? Looks like something arced or burned...
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Jordan...
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That's a reflection in the screening can ?.
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Mike G8GYW
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Mike,
([A=B] + POWER ON) should be a full reset, so you should be good there.
In your image what am I looking at (discolorization on the RF shielding); is that a burn mark?
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Random thoughts // questions:
1). Do you have an undervoltage situation (unit needs a bit more current to xmit, than rcv).? Maybe your PS is in need of a rest...
I'd carry the radio out to the car and see if I could get it into xmit into some dummy load at low power.
2). Or maybe your antenna feedline has a short.
3). Have you the right antenna selected?
4). I'd try removing and replacing the battery, then doing another FULL reset. I had read some posts in other places about this fixing similar problems.
5). Make sure all connectors (particularly the tiny coax ones are connected to their boards firmly).
6). Rx/Tx relay?
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This is a pretty interesting and informative video on troubleshooting the TS-570:
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Sam.
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Sorry - I now see you are asking about the 870s, not 570S.?
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Well this is frustrating ...
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I removed the screen cover from the Final unit to access the TX/RX relay and now it's working again ?.
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I couldn't see anything loose so I'm in the dark as to what's causing it.
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Maybe I just put it back together and see if it fails again.
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Incidentally what is the correct type of screwdriver for this radio? Posidriv, Philips or something else? I don't want to damage the pristine screws.
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Mike G8GYW
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All I can suggest is that you tighten all the
screws fixing the board to the chassis, then pull and then reseat the dc and
control like connectors...It could simply be an oxidized interconnection
contact. If it's a cold solder joint, that might require a little more work to
determine.?Intermittents can be a PITA...I use a Philips head screw driver.
Use one that fits snugly with no play...
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73...Jordan VE6ZT
----- Original Message -----
Sent: Thursday, March 13, 2025 7:25
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
Well this is frustrating ...
?
I removed the screen cover from the Final unit to access the TX/RX relay
and now it's working again ?.
?
I couldn't see anything loose so I'm in the dark as to what's causing
it.
?
Maybe I just put it back together and see if it fails again.
?
Incidentally what is the correct type of screwdriver for this radio?
Posidriv, Philips or something else? I don't want to damage the pristine
screws.
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Mike G8GYW
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P.S.....
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Should read "...control line
connectors."
----- Original Message -----
Sent: Thursday, March 13, 2025 7:55
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
All I can suggest is that you tighten all the
screws fixing the board to the chassis, then pull and then reseat the dc and
control like connectors...It could simply be an oxidized interconnection
contact. If it's a cold solder joint, that might require a little more work to
determine.?Intermittents can be a PITA...I use a Philips head screw
driver. Use one that fits snugly with no play...
?
73...Jordan VE6ZT
----- Original Message -----
Sent: Thursday, March 13, 2025 7:25
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
Well this is frustrating ...
?
I removed the screen cover from the Final unit to access the TX/RX
relay and now it's working again ?.
?
I couldn't see anything loose so I'm in the dark as to what's causing
it.
?
Maybe I just put it back together and see if it fails again.
?
Incidentally what is the correct type of screwdriver for this radio?
Posidriv, Philips or something else? I don't want to damage the pristine
screws.
?
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Mike G8GYW
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Thanks Jordan. All the board screws were tight and I couldn't see or feel any loose connectors but if/when it fails again I will follow your advice.
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This radio is immaculate and shows no signs of having been opened before. I think it may have been a demo model the dealer forgot about years ago and I may actually be its first owner.
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Mike G8GYW
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Ok Mike...No problem...have fun with the rig and
feel free to ask questions should you have any....73...Jordan VE6ZT
----- Original Message -----
Sent: Thursday, March 13, 2025 9:21
AM
Subject: Re: [Kenwood-Amateur-Radio]
TS-870S no TX
Thanks Jordan. All the board screws were tight and I couldn't see or feel
any loose connectors but if/when it fails again I will follow your
advice.
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This radio is immaculate and shows no signs of having been opened before.
I think it may have been a demo model the dealer forgot about years ago and I
may actually be its first owner.
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Mike G8GYW
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Mike,
Did you torque any screws on the board containing the Rx/Tx relay, or any metal shield covering portions of the circuitry?
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Sometimes these kinds of issues are caused by hairline fractures on a ckt board, and mechanically or thermally connections become intermittent. Mechanical Flakey.
Sometimes these kinds of issues are caused by cold solder joints, also impacted my mechanical or thermal stress. (Thermal Flakey).
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Now, it could be the Rx/Tx has pitted contacts such that the Common (c) center connection (Armature) does not shuttle between Normally Open (nc), and Normally Closed (nc) positions.
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Did you at least verify the Rx/Tx relay was firmly seated?
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Glad you got it working. Maybe it just wanted you to admire it from the inside.
Sam
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Bob