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Re: Syncal 30 RF/PA Transistor failure
I worked in Mobilcal engineering in the early 80s and as well as being part of the 4051 development got roped into looking at several of the HF PAs, 931, 4034, 4044.
Its a while since I did any HF design but as I recall one of the issues we had was that the HF PAs were necessarily broadband but over the frequency range the device input and output impedances would vary wildly.? Add to that the inter-stage ferrite transformers, an earth loop on the board or between the board and the chassis and a non-perfect load reflecting back into the output stage and trying to keep the whole line up stable across the band was challenging, achieved to some extent by heaps of feedback that wound back the gain of each stage.? One technique used for the higher power PAs was for the devices to be supplied against a Racal spec (a 'drawn item' in Racal lingo) in matched pairs but I don't recall if that was the case for the 931. ? ? Steve |
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Re: Syncal 30 RF/PA Transistor failure
Hi
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I do not know. But I guess the PA transistors were fragile in 1969 and they went to great lengths to protect them. Regards Ray vk2no That looks interesting Ray. |
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Re: Syncal 30 RF/PA Transistor failure
That looks interesting Ray.
That little voltage control board might just be what the Syncal needs. I am thinking it might be worth another try. But I struggle to see why they went to such trouble to limit the negative swing to a bit above 0V when just diodes to ground would have been almost as good. And I wonder if the consequence of that voltage limiting is that you now must have the fast current limit too as the voltage control puts the current up. M0GXB |
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Re: Syncal 30 RF/PA Transistor failure
Hi there,
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Regarding PA protection, attached is the circuit for the PA of a PRC-F1 It has 4 protection circuits in it. One is PA overcurrent protection One is PA overvoltage protection. These act directly on the PA transistors. There are 2 other protection circuits that act on the ALC control. I can send more pages that describe the operation if required, or you can download the entire EMEI from here... Regards ray There does indeed seem to be a design issue with the PA final stage in all |
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Re: Syncal 30 RF/PA Transistor failure
There does indeed seem to be a design issue with the PA final stage in all models of Syncal 30. I have had the misfortune to try and fail to repair this. I do have some clues on the failure. I suspect it is some kind of VHF resonance effect. The problem with Syncal 30 is that all the protection for the PA is "active" in that it involves feedback to control the drive. There is both a slow and fast ALC but this cannot be fast enough to deal with a signal outside of its normal frequency range or where the finals board is oscillating all by itself so that the drive is irrelevant. |
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Re: Syncal 30 RF/PA Transistor failure
Joe is well versed on the operation of the Syncal 30 so I'm sure a simple headphone change will not fix the problem on his #2 radio. The RF/PA failure is indeed an old subject that has appeared, and re-appeared, several times on a number of reflectors. No-body has ever come up with a viable explanation for the repeated failure of these devices. I was lucking in that I replaced mine once and have not needed to do it again, but as they failed for no apparent reason I am always very leery of operating the radio. KD0LTJ replaced his RF/PA transistors only to have them fail again the next time he used the radio. Dennis Starks Military-Radio-Guy KB?SFP HFpack/Milpack/MMRCG Monitor all: 3996usb, 5357usb, 7296usb, 14342.5usb, 18157.5usb, 29.4fm, 51.0fm MMRCG.org
On Sunday, November 17, 2019, 07:02:22 AM CST, Tony via Groups.Io <tony.helm@...> wrote:
Good Afternoon, Dennis and the Group ? I am very pleased to see this subject brought up again, as I have struggled with Syncal 30¡¯s for some years, having had a good run with them previously. ? Having actually met a man who was responsible for some of the design, if not all, of the Syncal 30, but who sadly isn¡¯t up to getting involved with them now he is not so young, I have got the impression that the design and build of the PA section was rather ¡°hit and miss¡±, and, once sold out to the purchaser, having passed through the factory tests, it was hit and miss how long they lasted. I have an XH which gave up the ghost on High Power years ago, has cost a good friend of mine a number of PA transistors with no result worth talking about, yet the ¡°Hopper section¡± is still working perfectly. It would be really good if this Winter we could liaise as a group and do some ¡°test and research¡± to see if we can find the reasons why. Low Output on AF on receive is a fairly simple problem to sort out, there is nothing odd about it, having first ensured that one is usi9ng the correct headphones. ? Good luck from Tony, G4BCX |
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Re: Syncal 30
¿ªÔÆÌåÓýGood Afternoon, Dennis and the Group ? I am very pleased to see this subject brought up again, as I have struggled with Syncal 30¡¯s for some years, having had a good run with them previously. ? Having actually met a man who was responsible for some of the design, if not all, of the Syncal 30, but who sadly isn¡¯t up to getting involved with them now he is not so young, I have got the impression that the design and build of the PA section was rather ¡°hit and miss¡±, and, once sold out to the purchaser, having passed through the factory tests, it was hit and miss how long they lasted. I have an XH which gave up the ghost on High Power years ago, has cost a good friend of mine a number of PA transistors with no result worth talking about, yet the ¡°Hopper section¡± is still working perfectly. It would be really good if this Winter we could liaise as a group and do some ¡°test and research¡± to see if we can find the reasons why. Low Output on AF on receive is a fairly simple problem to sort out, there is nothing odd about it, having first ensured that one is usi9ng the correct headphones. ? Good luck from Tony, G4BCX |
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Re: Syncal 30
The RF/PA transistors are high failure items. They are a mess to change as you must loose the roller inductor. RF Parts has the replacements. Dennis Starks Military-Radio-Guy KB?SFP HFpack/Milpack/MMRCG Monitor all: 3996usb, 5357usb, 7296usb, 14342.5usb, 18157.5usb, 29.4fm, 51.0fm MMRCG.org
On Friday, November 15, 2019, 12:05:17 PM CST, Joe Munson <prc74b@...> wrote:
I now have? 2 syncal 30 sets.? First set has no RF power out yet can be heard on close by receiver so assume low level driver stages working.?? Any Ideas as to where to start looking.? I figure finals probably shot.? Second set transmits fine, but very low audio out.? Any ideas on that.?? Thanks Joe Munson WA4VAG 513-919-1210 |
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Syncal 30
I now have? 2 syncal 30 sets.? First set has no RF power out yet can be heard on close by receiver so assume low level driver stages working.?? Any Ideas as to where to start looking.? I figure finals probably shot.? Second set transmits fine, but very low audio out.? Any ideas on that.??
Thanks Joe Munson WA4VAG 513-919-1210 |
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Re: new email
I think you'll need to change your address yourself. I tried to do it for you in this group and I get the message that the address is already in use. Dennis Starks Military-Radio-Guy KB?SFP HFpack/Milpack/MMRCG Monitor all: 3996usb, 5357usb, 7296usb, 14342.5usb, 18157.5usb, 29.4fm, 51.0fm MMRCG.org
On Monday, November 11, 2019, 06:34:52 AM CST, diasluiz22 <luizfdias@...> wrote:
Hello |
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Contributions
Yes I did get your contribution Ian and Thanks. I also received assistance from Ray Robinson,??Peter Gottlieb, and?Leighton Davies. Thanks to you guys too. We are still a bit short of recouping?expenses. Dennis Starks Military-Radio-Guy KB?SFP HFpack/Milpack/MMRCG Monitor all: 3996usb, 5357usb, 7296usb, 14342.5usb, 18157.5usb, 29.4fm, 51.0fm MMRCG.org
On Sunday, November 10, 2019, 05:00:53 PM CST, Ian Cooper <larkspu@...> wrote:
First, thanks to Dennis and Bob for completing this transfer. Dennis, did you get my contribution?? Regards,? Ian Cooper |
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New file uploaded to [email protected]
[email protected] Notification
Hello, This email message is a notification to let you know that the following files have been uploaded to the Files area of the [email protected] group. Uploaded By: Dennis <spike.dennis@...> Description: Cheers, |
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New file uploaded to [email protected]
[email protected] Notification
Hello, This email message is a notification to let you know that the following files have been uploaded to the Files area of the [email protected] group. Uploaded By: Dennis <spike.dennis@...> Description: Cheers, |
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A better cover photo and Groups IO fees
1st I'd like input on the group's cover photo. The one currently there really isnt well suited. I hate groups that neglect to display a cover photo so I slapped that one up there as it was handy. I'm asking for suggestions as to it's replacement. Maybe a Syncal 30 is actual field use or something.?/g/RacalRadio 2nd, I find this a bit distasteful, so I waited until after the transfer was complete. I need to address the issue of fees. Bob & I had to act quickly to get the group transferred. We were lucky in that we were able to get the new IO group created and upgraded to premium only minutes before the fee double to $220. We are all set for a year and if we stay under 1gig of usage we can downgrade to a free group next year. That is provided Groups IO doesnt change their minds. Currently we are just under 600mb of usage so we're safe for now. If Groups IO does change it's mind we still have a contingency plan. If you'd like to make a contribution to the expenses, please consider sending a few dollars via paypal friends & family to the below address. Indicate what group it is your helping. spike dot dennis at yahoo dot com Thanks Dennis Starks Military-Radio-Guy KB?SFP HFpack/Milpack/MMRCG Monitor all: 3996usb, 5357usb, 7296usb, 14342.5usb, 18157.5usb, 29.4fm, 51.0fm MMRCG.org |
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Fw: Your group has been transfered
Finally, it's all done. This should be the last message over the old yahoo group. Please address all future traffic to the new IO group at: /g/RacalRadio At this point the owner of the original yahoo group should shut off all messaging and stop uploads of data to prevent the loss of information. A notice should be placed in the groups home page descriptive text to notifying all those who find it of our move to Groups IO, and post the above link. This way, even though the old yahoo group will be dead it may still act as a sign post to direct people here. You can see the details of the transfer below. "Live Long and Prosper" Dennis KB0SFP Hello, The transfer of your Yahoo Group racal-manpacks to your Groups.io group RacalRadio is complete. We've transferred the following parts of your group:
IMPORTANT: Yahoo Groups has been very unreliable lately. If you find that you are missing Photos, Files or Messages, it is because we were unable to export them due to problems with Yahoo Groups. Also, we do not transfer calendar events. Here are some statistics:
313 photos were transferred. 93 files were transferred. 18 links were transferred. WARNING: Some links were not able to be transferred because of a bug in Yahoo's export system. You will need to manually review the links. 0 databases were transferred. If you have any questions, please contact [email protected]. If you don't anticipate retrying the transfer, please remove the [email protected] member from your Yahoo Group. Cheers, |
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Re: Racal Move to Groups IO
On behalf of the Group, I would like to thank Dennis for all the work he has put in to achieve this! Bob, G8IYK
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Racal Move to Groups IO
This yahoo group will shortly be moved lock, sock, and barrel, to Groups IO. The new Racal Groups IO was created then upgraded to premium status just minutes before the cost was doubled. All the archives, files, pictures, and mailing list will be automatically imported into the new group. You dont need to do anything. As yahoo groups are currently erratic, and Groups IO is swapped with transfer request, this process may take a week or so. If you cant wait, you can sign up at the below address. In the mean time, we did incur a cost of $110 for the transfer. Donations to offset this expense would be greatly appreciate. Please consider a minimal donation via paypal friends/family to the below address. Indicated the group you are helping to save: spike dot dennis at yahoo dot com Thanks Dennis? KB?SFP? |
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Re: Digest Number 1856
¿ªÔÆÌåÓýYou pay one way or another. No free lunch etc. With yahoo you get ads and them selling your info, with groups.io you pay directly. Go to Google and they sell and use your info again. Any of these indirect supported ones are subject to cancellation at any time the suits decide the income isn¡¯t enough. If a service like groups.io makes money via their direct pay model, they are more likely to remain in business, although the suits may keep increasing the price.?Peter On Oct 24, 2019, at 6:30 AM, Mike M1CCF@... [Racal-manpacks] wrote:
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