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Peter,

Thanks for your reply.

Yes, I have read the manual, finally, but not completely yet. I now know that I must be in SSB when looking for the 1.4 MHz signal at the test point.

I do see the signal there 'rich in harmonics' as the manual states. Attached is the picture.

Unfortunately there doesn't seem to be a voltage checklist for the active components on the Syntheszier board like there is for the Transceiver board so this may make things a bit more difficult for me.

Thanks for the help and interest.

Dave KC3AM

Dave,

It sounds as if you are making some progress. Did you read the manual on how the 1.4 MHz signal is generated? If you are in AM Rx it seems that the 1.4 MHz signal is muted (see Part 3 page 2-9), so could be why you are not seeing that signal? Change to USB or LSB and see if the 1.4MHz signal returns,. If not, then you have a good place to start looking for faults.

73,

Peter
G4DJB

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Richard,

Thank you very much for this info and making it available.

I have a TRA-931 that I am trying to repair although I feel like it is somewhat above my ability.

The availability of the manual was the biggest encouragement at the start.

I have had an offer of help through e-mail to try to repair this unit and it is slow going.

I notice in the manual that there is a table for voltages on the Transceiver board but not for the Synthesizer board which is sad.

Is there anyone who repairs these?

Thanks again for the work you have done.

Dave KC3AM

Folks,

just to clarify the point below about the manuals on the vmars website.?? These are still free for anyone to access, without a password, membership or anything else.??? I was the first archivist and argued for free access to all manuals on the basis that this is historical information not "owned" by anyone - and wide distribution is the best way to ensure the survival of this information long after most of the world has entirely forgotten about it.??? And I am pleased to see it remains free to access today.

The TRA-931 manual is at:

and I am amused to see it has my name on it together with credits to the people who supplied the information in hard copy.

Richard

G7RVI

On 14/07/2020 20:45, Dave via groups.io wrote:

More pictures.

On 07/13/2020 08:48, John Whitehouse via groups.io wrote:

??

Hi Dave,

Its been a while since I worked on TRA931???s like well over 40 years ago now, but I do own several TRA931???s and have had to maintain them from time to time. The TRA931 was probably Racal???s best-selling radio ever, literally thousands were made and sold worldwide. They were designed as an export radio using quality components to meeting MIL spec but without all the paperwork and qualification that went will producing a radio for NATO use. The TRA931 has and still is used from the Artic/Antarctic to the jungles of South America/Africa to the deserts of the Middle east. It coped well win these environments and beat all its competition on price and performance. The TRA931 was produced from the early 1970???s until Racal was taken over in 2000 and was a great seller for all this time. Saying it was an export radio did not stop NATO governments purchasing quantities of TRA931???s for there own use so the radio proved to be a well liked and requested radio worldwide.

??

Firstly, the TRA931 operates from a nominal 24Vdc supply, typically you can go down to 18V and even lower on receive and up to about 30Vdc. If you go higher than 30V the 33v Zenner diode D3 mounted on the main chassis will cause the 7A fuse FS1 to blow thus protecting the radio from over voltage.

Secondly in the era when these sets were made Tantalum capacitors where a new technology and proved over the years not to be reliable. They will fail for what appears to be no reason and I would recommend you change them all in your radio if you can. I have done this with my own TRA931. Depending on the age of your TRA931 you may not have any tantalum capacitors at all as the earlier TRA931???s did not have any tantalum capacitors.

You need to find yourself a copy of the TRA931 handbook (if you don???t already have one) so you can access the schematic diagrams to make fault finding somewhat easier. The VMARS website in the UK () has many Racal handbooks available to download but I am not certain if you have to be a member to access the manual section of the website.

You do not say if the fault is just limited to Tx path or if you have problems on receive as well? If the radio is receiving correctly a lot of the common circuitry can be eliminated from your fault-finding analysis. If your fault is common to both Tx and Rx there are common areas like 1.4Mhz switching where one should start one???s investigations.

When you say L16 went up in smoke and C62 shorted I am assuming you are referring to the Synthesiser board MA925? This issue being for example C62 is not C62 for the radio but C62 just on the Synthesiser board. When specifying a component or test point, you also have to say what board it is from or even if it???s a chassis component as the boards where used in other products as well as the TRA931 so you can have multiple references say to a R12 or TP11 in a particular radio.

The only L16 I could find was on the synthesiser board and assume the C62 was also as if C62 shorted L16 would go up in smoke as you experienced. The Synthesiser board has three outputs one at 1.4Mhz (pins 61 & 62) one at 34Mhz (Pins 58 &59) and the Main variable output (Pins 41 & 42) so it is worth just checking they are all present before continuing your fault finding further.

The TP1 you refer to on what board is it? As the only TP1 I have found so far is on the transceiver board and this is on the antenna side of the channel mixer after the band pass filter?

Also what mode are you using when you measure the power output? If you are measuring it in ???Tune??? I would have expected to see 4 to 6W output.

The PA board transistors often did not have a connection to the ???collector pin??? as the connection was made through the stud (also connected to the collector) maybe someone else out there has knowledge of this and will let you know.

Loosing the 1.4Mhz in the Tx path on the Transceiver board can give you some of the symptoms you are experiencing. There are multiple 1.4Mhz switching points and PTT switching using 1N4149 diodes which I have experienced problems with over the years. I have had these simply just fail or more commonly exhibit a high leakage current so you should exhibit some suspicion of these diodes if they are located anywhere near part of the circuit you are testing. You also need to check the PTT switching as a 12V rail may be missing and causing your issues there are multiple PSU regulator circuits on each board so they all have to be checked as functional before proceeding further with your fault-finding.

??

I am sorry I cannot be of more help in this email, I do hope you can find the fault as the TRA931 is a radio worth saving and using.

Please let me know how you get on with your investigations and I will be happy to help you further and have email discussions with you to help you fault find the radio.

??

Best regards

??

John G6LJU

-----Original Message-----
From: Dave via groups.io <kc3am@...>
To: [email protected]
Sent: Sat, 11 Jul 2020 1:50
Subject: Re: [RacalRadio] just joined, need assistance with a deaf Syncal 30

Hello John,
Dave here KC3AM and I am asking for some help. From your comments above maybe you can help me some with my TRA931 that I got from a friend who is now a SK.

Not knowing anything about this radio when I got it I found out that I needed 24 VDC for power. I originally powered it up from a 12 VDC supply and saw that it did come to life and seemed to RX OK. I then tried it at 18 VDC and had about 4 watts RF out. I brought it up to 23 VDC?? and all seemed well. Then the smoke came out. In the power supply section. C 62 apparently shorted and L16 went up in smoke. These were easy to find since they were blackened. They have been exactly replaced. 5, 9, 15 VDC all seem to be fine now but I have very little RF out now, not my 4 watts. (This is where I found another problem. On the PA board TR2 is has the collector lead missing which is probably one reason for the low initial output.) I cannot get my initial 4 watts output now. Hooking the 3 - 30 BNC jack to a Motorola service monitor I do see an output signal exactly on frequency so the synth board is OK and at TP1 I have the 8 MHz signal that matches the front panel setting. I am using an old Motorola RF voltmeter to look for RF. AT TP1 I have about 1/10 VDC. At the output of the wideband amp at A21 I have about the same. Looking at the static voltage chart TR 33 & 32 look OK, TR31 I start with 24 VDC and only drops to 20VDC upon transmit on the collector. TR31 looks OK but I am planning on replacing it anyway. All voltages that I have looked at seem to be OK, 12TX ,24PA.

Can you offer any suggestions?

Thank you very much for your time.
Dave KC3AM

--
73, Dave KC3AM

开云体育

Folks,

just to clarify the point below about the manuals on the vmars website.?? These are still free for anyone to access, without a password, membership or anything else.??? I was the first archivist and argued for free access to all manuals on the basis that this is historical information not "owned" by anyone - and wide distribution is the best way to ensure the survival of this information long after most of the world has entirely forgotten about it.??? And I am pleased to see it remains free to access today.

The TRA-931 manual is at:

and I am amused to see it has my name on it together with credits to the people who supplied the information in hard copy.

Richard

G7RVI

开云体育

More pictures.

??

Hi Dave,

Its been a while since I worked on TRA931???s like well over 40 years ago now, but I do own several TRA931???s and have had to maintain them from time to time. The TRA931 was probably Racal???s best-selling radio ever, literally thousands were made and sold worldwide. They were designed as an export radio using quality components to meeting MIL spec but without all the paperwork and qualification that went will producing a radio for NATO use. The TRA931 has and still is used from the Artic/Antarctic to the jungles of South America/Africa to the deserts of the Middle east. It coped well win these environments and beat all its competition on price and performance. The TRA931 was produced from the early 1970???s until Racal was taken over in 2000 and was a great seller for all this time. Saying it was an export radio did not stop NATO governments purchasing quantities of TRA931???s for there own use so the radio proved to be a well liked and requested radio worldwide.

??

Firstly, the TRA931 operates from a nominal 24Vdc supply, typically you can go down to 18V and even lower on receive and up to about 30Vdc. If you go higher than 30V the 33v Zenner diode D3 mounted on the main chassis will cause the 7A fuse FS1 to blow thus protecting the radio from over voltage.

Secondly in the era when these sets were made Tantalum capacitors where a new technology and proved over the years not to be reliable. They will fail for what appears to be no reason and I would recommend you change them all in your radio if you can. I have done this with my own TRA931. Depending on the age of your TRA931 you may not have any tantalum capacitors at all as the earlier TRA931???s did not have any tantalum capacitors.

You need to find yourself a copy of the TRA931 handbook (if you don???t already have one) so you can access the schematic diagrams to make fault finding somewhat easier. The VMARS website in the UK () has many Racal handbooks available to download but I am not certain if you have to be a member to access the manual section of the website.

You do not say if the fault is just limited to Tx path or if you have problems on receive as well? If the radio is receiving correctly a lot of the common circuitry can be eliminated from your fault-finding analysis. If your fault is common to both Tx and Rx there are common areas like 1.4Mhz switching where one should start one???s investigations.

When you say L16 went up in smoke and C62 shorted I am assuming you are referring to the Synthesiser board MA925? This issue being for example C62 is not C62 for the radio but C62 just on the Synthesiser board. When specifying a component or test point, you also have to say what board it is from or even if it???s a chassis component as the boards where used in other products as well as the TRA931 so you can have multiple references say to a R12 or TP11 in a particular radio.

The only L16 I could find was on the synthesiser board and assume the C62 was also as if C62 shorted L16 would go up in smoke as you experienced. The Synthesiser board has three outputs one at 1.4Mhz (pins 61 & 62) one at 34Mhz (Pins 58 &59) and the Main variable output (Pins 41 & 42) so it is worth just checking they are all present before continuing your fault finding further.

The TP1 you refer to on what board is it? As the only TP1 I have found so far is on the transceiver board and this is on the antenna side of the channel mixer after the band pass filter?

Also what mode are you using when you measure the power output? If you are measuring it in ???Tune??? I would have expected to see 4 to 6W output.

The PA board transistors often did not have a connection to the ???collector pin??? as the connection was made through the stud (also connected to the collector) maybe someone else out there has knowledge of this and will let you know.

Loosing the 1.4Mhz in the Tx path on the Transceiver board can give you some of the symptoms you are experiencing. There are multiple 1.4Mhz switching points and PTT switching using 1N4149 diodes which I have experienced problems with over the years. I have had these simply just fail or more commonly exhibit a high leakage current so you should exhibit some suspicion of these diodes if they are located anywhere near part of the circuit you are testing. You also need to check the PTT switching as a 12V rail may be missing and causing your issues there are multiple PSU regulator circuits on each board so they all have to be checked as functional before proceeding further with your fault-finding.

??

I am sorry I cannot be of more help in this email, I do hope you can find the fault as the TRA931 is a radio worth saving and using.

Please let me know how you get on with your investigations and I will be happy to help you further and have email discussions with you to help you fault find the radio.

??

Best regards

??

John G6LJU

-----Original Message-----
From: Dave via groups.io <kc3am@...>
To: [email protected]
Sent: Sat, 11 Jul 2020 1:50
Subject: Re: [RacalRadio] just joined, need assistance with a deaf Syncal 30

Hello John,
Dave here KC3AM and I am asking for some help. From your comments above maybe you can help me some with my TRA931 that I got from a friend who is now a SK.

Not knowing anything about this radio when I got it I found out that I needed 24 VDC for power. I originally powered it up from a 12 VDC supply and saw that it did come to life and seemed to RX OK. I then tried it at 18 VDC and had about 4 watts RF out. I brought it up to 23 VDC?? and all seemed well. Then the smoke came out. In the power supply section. C 62 apparently shorted and L16 went up in smoke. These were easy to find since they were blackened. They have been exactly replaced. 5, 9, 15 VDC all seem to be fine now but I have very little RF out now, not my 4 watts. (This is where I found another problem. On the PA board TR2 is has the collector lead missing which is probably one reason for the low initial output.) I cannot get my initial 4 watts output now. Hooking the 3 - 30 BNC jack to a Motorola service monitor I do see an output signal exactly on frequency so the synth board is OK and at TP1 I have the 8 MHz signal that matches the front panel setting. I am using an old Motorola RF voltmeter to look for RF. AT TP1 I have about 1/10 VDC. At the output of the wideband amp at A21 I have about the same. Looking at the static voltage chart TR 33 & 32 look OK, TR31 I start with 24 VDC and only drops to 20VDC upon transmit on the collector. TR31 looks OK but I am planning on replacing it anyway. All voltages that I have looked at seem to be OK, 12TX ,24PA.

Can you offer any suggestions?

Thank you very much for your time.
Dave KC3AM

开云体育

Hello there John,

Thank you for your time and reply. You seem like a wealth of information.

I will try to comment within your response.

?

Hi Dave,

Its been a while since I worked on TRA931’s like well over 40 years ago now, but I do own several TRA931’s and have had to maintain them from time to time. The TRA931 was probably Racal’s best-selling radio ever, literally thousands were made and sold worldwide. They were designed as an export radio using quality components to meeting MIL spec but without all the paperwork and qualification that went will producing a radio for NATO use. The TRA931 has and still is used from the Artic/Antarctic to the jungles of South America/Africa to the deserts of the Middle east. It coped well win these environments and beat all its competition on price and performance. The TRA931 was produced from the early 1970’s until Racal was taken over in 2000 and was a great seller for all this time. Saying it was an export radio did not stop NATO governments purchasing quantities of TRA931’s for there own use so the radio proved to be a well liked and requested radio worldwide.

?

Firstly, the TRA931 operates from a nominal 24Vdc supply, typically you can go down to 18V and even lower on receive and up to about 30Vdc. If you go higher than 30V the 33v Zenner diode D3 mounted on the main chassis will cause the 7A fuse FS1 to blow thus protecting the radio from over voltage.

Secondly in the era when these sets were made Tantalum capacitors where a new technology and proved over the years not to be reliable. They will fail for what appears to be no reason and I would recommend you change them all in your radio if you can. I have done this with my own TRA931. Depending on the age of your TRA931 you may not have any tantalum capacitors at all as the earlier TRA931’s did not have any tantalum capacitors.

You need to find yourself a copy of the TRA931 handbook (if you don’t already have one) so you can access the schematic diagrams to make fault finding somewhat easier. The VMARS website in the UK () has many Racal handbooks available to download but I am not certain if you have to be a member to access the manual section of the website.

You do not say if the fault is just limited to Tx path or if you have problems on receive as well? If the radio is receiving correctly a lot of the common circuitry can be eliminated from your fault-finding analysis. If your fault is common to both Tx and Rx there are common areas like 1.4Mhz switching where one should start one’s investigations.

When you say L16 went up in smoke and C62 shorted I am assuming you are referring to the Synthesiser board MA925? This issue being for example C62 is not C62 for the radio but C62 just on the Synthesiser board. When specifying a component or test point, you also have to say what board it is from or even if it’s a chassis component as the boards where used in other products as well as the TRA931 so you can have multiple references say to a R12 or TP11 in a particular radio.

The only L16 I could find was on the synthesiser board and assume the C62 was also as if C62 shorted L16 would go up in smoke as you experienced.

The Synthesiser board has three outputs one at 1.4Mhz (pins 61 & 62) one at 34Mhz (Pins 58 &59) and the Main variable output (Pins 41 & 42) so it is worth just checking they are all present before continuing your fault finding further.

The TP1 you refer to on what board is it? As the only TP1 I have found so far is on the transceiver board and this is on the antenna side of the channel mixer after the band pass filter?

Yes, that is the TP1 I have looked at as well as TP10 to verify signal thru the relay.

..... Looking at static voltages for TR 33, 32, 31 on the Transceiver board. TR 33 & 32 are close to what the manual indicates, 31 bothers me. In RX mode Collector voltage is 24 VDC in TX it only drops to about 20 VDC. The manual says it should be about 11 VDC in TX mode. It also has a heat sink and is stone cold. I pulled it out for testing and is seemed OK but I have replaced it anyway with no change in operation.

Also what mode are you using when you measure the power output? If you are measuring it in “Tune” I would have expected to see 4 to 6W output.

The PA board transistors often did not have a connection to the ‘collector pin’ as the connection was made through the stud (also connected to the collector) maybe someone else out there has knowledge of this and will let you know.

Loosing the 1.4Mhz in the Tx path on the Transceiver board can give you some of the symptoms you are experiencing. There are multiple 1.4Mhz switching points and PTT switching using 1N4149 diodes which I have experienced problems with over the years. I have had these simply just fail or more commonly exhibit a high leakage current so you should exhibit some suspicion of these diodes if they are located anywhere near part of the circuit you are testing.

You also need to check the PTT switching as a 12V rail may be missing and causing your issues there are multiple PSU regulator circuits on each board so they all have to be checked as functional before proceeding further with your fault-finding.

?

I am sorry I cannot be of more help in this email, I do hope you can find the fault as the TRA931 is a radio worth saving and using.

Please let me know how you get on with your investigations and I will be happy to help you further and have email discussions with you to help you fault find the radio.

You have been a great help with this info John. I will start looking at the 1.4 MHz circuit. I am looking at the frequency in a crude way. I am just using the RF input to the Motorola service monitor and a little sniffer wire. The 34 MHz looked proper doing it this way but the 1.4 MHz looks horrible as you can see.

I will keep you informed.

Again Thank You very much for your help

Dave KC3AM

?

Best regards

?

John G6LJU

-----Original Message-----
From: Dave via groups.io <kc3am@...>
To: [email protected]
Sent: Sat, 11 Jul 2020 1:50
Subject: Re: [RacalRadio] just joined, need assistance with a deaf Syncal 30

Hello John,
Dave here KC3AM and I am asking for some help. From your comments above maybe you can help me some with my TRA931 that I got from a friend who is now a SK.

Not knowing anything about this radio when I got it I found out that I needed 24 VDC for power. I originally powered it up from a 12 VDC supply and saw that it did come to life and seemed to RX OK. I then tried it at 18 VDC and had about 4 watts RF out. I brought it up to 23 VDC? and all seemed well. Then the smoke came out. In the power supply section. C 62 apparently shorted and L16 went up in smoke. These were easy to find since they were blackened. They have been exactly replaced. 5, 9, 15 VDC all seem to be fine now but I have very little RF out now, not my 4 watts. (This is where I found another problem. On the PA board TR2 is has the collector lead missing which is probably one reason for the low initial output.) I cannot get my initial 4 watts output now. Hooking the 3 - 30 BNC jack to a Motorola service monitor I do see an output signal exactly on frequency so the synth board is OK and at TP1 I have the 8 MHz signal that matches the front panel setting. I am using an old Motorola RF voltmeter to look for RF. AT TP1 I have about 1/10 VDC. At the output of the wideband amp at A21 I have about the same. Looking at the static voltage chart TR 33 & 32 look OK, TR31 I start with 24 VDC and only drops to 20VDC upon transmit on the collector. TR31 looks OK but I am planning on replacing it anyway. All voltages that I have looked at seem to be OK, 12TX ,24PA.

Can you offer any suggestions?

Thank you very much for your time.
Dave KC3AM

Tom

thank you! I didn't notice the attachment so i went ahead and made a simple 3 tr 1W amp. Got terrible issues with
RF getting into my audio amp. By passing the audio input side didn't help and also the DC power from the radio. The schematic you kindly posted has a mute feature tied to the PTT.
I think they must have had the same problem!
?I will add that feature to my amp
Thanks!

Peter