Trio TR-9000 - Help Needed - UK Vintage Radio Repair and Restoration Discussion Forum

totalamateur · 20th Jul 2021, 2:05 pm

Good afternoon,

This is my first post here and hope you are all well.

I have been in amateur radio for a little while and have recently acquired a Trio/Kenwood TR-9000 and need to seek some advice on the following issues:

Firstly everything on the radio functions as intended with two minor problems.

1) SSB Is fine at first but the audio quality drops away to becoming flat and 'gravelly' but this happens without any loss of actual RF Power/Output and takes place over time.

2) Small display showing the frequency intermittently changes to 6.000-7.999 range instead of the usual 4.000-5.999 ranges. As far as I can tell this is clearly erroneous as the transceiver itself still functions as if on the previously set frequency.

I have been doing some research into how to fix this however information seems to be fairly limited.

Would appreciate any advice or directions you can give, the radio was purchased cheaply and is in great shape and has been looked after well. It is mounted on the Kenwood system base.

Many thanks

mickm3for · 20th Jul 2021, 4:45 pm

Hi had the display problem on 3x this rig found dry joints on display board double side board, the Service Manual is here:-

https://elektrotanya.com/kenwood_tr-.../download.html

Is the audio on RX or only TX SSB and if you tune a little to either side does it clear? ie is it drifting?

Welcome, Mick.

Outposter30 · 20th Jul 2021, 8:58 pm

The TR-9xxx series all had problems with solder joints and trace failure, usually due to corrosion and poor pre-solder preparation at the time of production.

They are nice rigs when working properly...!

73...Jordan VE6ZT

Andrew2 · 21st Jul 2021, 10:56 am

The 'gravelly' SSB TX could well be our old friend the Misubishi PA module. It will still sound OK on FM as FM doesn't need a linear amplifier, but SSB will become spiky and unpleasant. The fault can be intermittent/random or it can go with temperature.
I'm not sure, but you may be able to get a modern type to fit with a bit of furtling. Last time I looked, GH engineering sold them and if you ask nicely he will advise.

http://www.ghengineering.co.uk/products/Mitsubishi.htm

I've just had a look and none of the modules are labelled as suitable for SSB, so you may have to prod him for details.

Radio Wrangler · 21st Jul 2021, 11:37 am

If it is the mitsubishi PA block, the plastic cover can be cut off with a fine bladed modelling saw. Careful inspection with a microscope (and sometimes with a multimeter on Ohms bleep) can find the crack in the substrate. With great care, the metal track can have wires soldered over the cracks.

If you're very unlucky the crack might have split a thick-film resistor area. If so a bit of messing around may give an idea of the value, the resistor can be deliberately ruined to open circuit it and a wire-ended one shaped to bridge it.

I've also bridged in diodes this way.

The PA and driver transistors are mounted through holes in the ceramic substrate onto the copper bar.

David

Richard675 · 22nd Jul 2021, 12:01 pm

1) SSB Is fine at first but the audio quality drops away to becoming flat and 'gravelly' but this happens without any loss of actual RF Power/Output

………..Check on TX that the Bias voltage is as it should be. Mine is/was 8v. This can be done without opening the module, I think it’s pin 3 on the M57727.

………..You could consider disconnecting the input to the module and monitor a tx test on another receiver briefly. This should tell you if the problem is in the module or further back on the main board.

2) Small display showing the frequency intermittently changes to 6.000-7.999 range instead of the usual 4.000-5.999 ranges. As far as I can tell this is clearly erroneous as the transceiver itself still functions as if on the previously set frequency.

……..this could be due to a legacy job on the band programming diodes. Back in the day some owners were “opening up” their 2m radios to cover the full 4 Megs. All sorts of interesting stuff above 146 at the time…..(so I was told)

…….On a Kenwood I had of that era were a group of 4 diodes hidden somewhere. I found them within the front panel PCB. Be prepared for some dismantling. The radio will probably need a reset if there is such an option on your set.

…….You need to study the circuit diagram which should tell you somewhere what diodes you need for 144 - 146 MHz and not 144-148.

totalamateur · 22nd Jul 2021, 1:21 pm

Thank you for all the replies:

I Have noted that the chips is unavailable and was hoping that it would not be this. Will have to have a look in further detail using the suggestions above and get back to you.

Just to clarify it is the SSB TX Audio that is the problem the set receives perfectly on all modes. and transmits without issue on all others.

Thanks again

Radio Wrangler · 22nd Jul 2021, 3:00 pm

Much of the receiver stuff is shared with the transmitter and microphone amps are shared with FM.

I think, as suggested before, things do point to the PA module.

The suggestion to disconnect the module and try another SSB receiver near it to assess the modulation quality before the PA is excellent.

David

Jon_G4MDC · 22nd Jul 2021, 10:56 pm

I would try the poor man's spectrum analyser on that - if you have one.

The SDR dongles such as this will let you see what is going on if you can just loosely couple one to the output. A short sense wire is probably enough.

If you have one, and you want to try it, post back here. I won't launch off into suggestions unless it's worthwhile.

https://www.rtl-sdr.com/wp-content/u...?ffccfa&ffccfa

20th Jul 2021, 2:05 pm	#1
totalamateur Diode Join Date: Jul 2021 Location: Fareham, Hampshire, UK. Posts: 2	Trio TR-9000 - Help Needed Good afternoon, This is my first post here and hope you are all well. I have been in amateur radio for a little while and have recently acquired a Trio/Kenwood TR-9000 and need to seek some advice on the following issues: Firstly everything on the radio functions as intended with two minor problems. 1) SSB Is fine at first but the audio quality drops away to becoming flat and 'gravelly' but this happens without any loss of actual RF Power/Output and takes place over time. 2) Small display showing the frequency intermittently changes to 6.000-7.999 range instead of the usual 4.000-5.999 ranges. As far as I can tell this is clearly erroneous as the transceiver itself still functions as if on the previously set frequency. I have been doing some research into how to fix this however information seems to be fairly limited. Would appreciate any advice or directions you can give, the radio was purchased cheaply and is in great shape and has been looked after well. It is mounted on the Kenwood system base. Many thanks

20th Jul 2021, 4:45 pm	#2
mickm3for Heptode Join Date: May 2015 Location: Chatham, Kent, UK. Posts: 963	Re: Trio TR-9000 - Help Needed Hi had the display problem on 3x this rig found dry joints on display board double side board, the Service Manual is here:- https://elektrotanya.com/kenwood_tr-.../download.html Is the audio on RX or only TX SSB and if you tune a little to either side does it clear? ie is it drifting? Welcome, Mick.

20th Jul 2021, 8:58 pm	#3
Outposter30 Triode Join Date: Oct 2020 Location: Calgary, Alberta, Canada. Posts: 22	Re: Trio TR-9000 - Help Needed The TR-9xxx series all had problems with solder joints and trace failure, usually due to corrosion and poor pre-solder preparation at the time of production. They are nice rigs when working properly...! 73...Jordan VE6ZT

21st Jul 2021, 10:56 am	#4
Andrew2 Nonode Join Date: Mar 2010 Location: Dukinfield, Cheshire, UK. Posts: 2,037	Re: Trio TR-9000 - Help Needed The 'gravelly' SSB TX could well be our old friend the Misubishi PA module. It will still sound OK on FM as FM doesn't need a linear amplifier, but SSB will become spiky and unpleasant. The fault can be intermittent/random or it can go with temperature. I'm not sure, but you may be able to get a modern type to fit with a bit of furtling. Last time I looked, GH engineering sold them and if you ask nicely he will advise. http://www.ghengineering.co.uk/products/Mitsubishi.htm I've just had a look and none of the modules are labelled as suitable for SSB, so you may have to prod him for details. __________________ Andy G1HBE. Last edited by Andrew2; 21st Jul 2021 at 11:01 am.

21st Jul 2021, 11:37 am	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,867	Re: Trio TR-9000 - Help Needed If it is the mitsubishi PA block, the plastic cover can be cut off with a fine bladed modelling saw. Careful inspection with a microscope (and sometimes with a multimeter on Ohms bleep) can find the crack in the substrate. With great care, the metal track can have wires soldered over the cracks. If you're very unlucky the crack might have split a thick-film resistor area. If so a bit of messing around may give an idea of the value, the resistor can be deliberately ruined to open circuit it and a wire-ended one shaped to bridge it. I've also bridged in diodes this way. The PA and driver transistors are mounted through holes in the ceramic substrate onto the copper bar. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

22nd Jul 2021, 12:01 pm	#6
Richard675 Pentode Join Date: Jun 2009 Location: Braintree, Essex, UK. Posts: 170	Re: Trio TR-9000 - Help Needed 1) SSB Is fine at first but the audio quality drops away to becoming flat and 'gravelly' but this happens without any loss of actual RF Power/Output ………..Check on TX that the Bias voltage is as it should be. Mine is/was 8v. This can be done without opening the module, I think it’s pin 3 on the M57727. ………..You could consider disconnecting the input to the module and monitor a tx test on another receiver briefly. This should tell you if the problem is in the module or further back on the main board. 2) Small display showing the frequency intermittently changes to 6.000-7.999 range instead of the usual 4.000-5.999 ranges. As far as I can tell this is clearly erroneous as the transceiver itself still functions as if on the previously set frequency. ……..this could be due to a legacy job on the band programming diodes. Back in the day some owners were “opening up” their 2m radios to cover the full 4 Megs. All sorts of interesting stuff above 146 at the time…..(so I was told) …….On a Kenwood I had of that era were a group of 4 diodes hidden somewhere. I found them within the front panel PCB. Be prepared for some dismantling. The radio will probably need a reset if there is such an option on your set. …….You need to study the circuit diagram which should tell you somewhere what diodes you need for 144 - 146 MHz and not 144-148.

22nd Jul 2021, 1:21 pm	#7
totalamateur Diode Join Date: Jul 2021 Location: Fareham, Hampshire, UK. Posts: 2	Re: Trio TR-9000 - Help Needed Thank you for all the replies: I Have noted that the chips is unavailable and was hoping that it would not be this. Will have to have a look in further detail using the suggestions above and get back to you. Just to clarify it is the SSB TX Audio that is the problem the set receives perfectly on all modes. and transmits without issue on all others. Thanks again

22nd Jul 2021, 3:00 pm	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,867	Re: Trio TR-9000 - Help Needed Much of the receiver stuff is shared with the transmitter and microphone amps are shared with FM. I think, as suggested before, things do point to the PA module. The suggestion to disconnect the module and try another SSB receiver near it to assess the modulation quality before the PA is excellent. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

22nd Jul 2021, 10:56 pm	#9
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: Trio TR-9000 - Help Needed I would try the poor man's spectrum analyser on that - if you have one. The SDR dongles such as this will let you see what is going on if you can just loosely couple one to the output. A short sense wire is probably enough. If you have one, and you want to try it, post back here. I won't launch off into suggestions unless it's worthwhile. https://www.rtl-sdr.com/wp-content/u...?ffccfa&ffccfa