How to change the frequency on one of these transmitter boxes.

[ehsanspicedigital]

Hello lads. Hope your all doin well. I’ve got one of these transmitter boxes made by a well known rig builder . just wanted to ask if anyone knows how to accurately tune the frequency on this unit. I think it’s somewhere in the driver box, but i don’t know exactly what to do in there. If someone could please guide me it’d be extremely appreciated. Thanks

[Frequent Lee]

They are locked to one frequency, the driver will need the pic chip replaced with one programmed to the frequency of choice and the ppl lock can adjusted also the amp will need to be returned to match the new frequency so the output isn't mismatched.
If you're Yorkshire based that rig will have come via me originally as I was the only person in the north dealing with that builder.

[ehsanspicedigital]

Sent you a PM

[teckniqs]

Ooops...

Jel burned out 1.jpg

Jel burned out 2.jpg

[ehsanspicedigital]

How did this happen!!

[teckniqs]

I have no idea, all I know was the SWR on their aerial was fine and not the cause.
.... I was given that board by someone from London to repair, but it was as you can see knackered, amazingly though both of the transistors still worked so they were removed for use on another fresh board.

Jel burned out 3.jpg

Jel burned out 4.jpg

[rigmo]

lighting or hiSWR

[ehsanspicedigital]

i’ve seen a few mishaps with this board in specific and now i’m questioning what could cause this! Could it be a board defect in certain PCB’s not being made up to standard or something to do with the components on the board not being rated for the power output? Or even using incorrectly rated FET’s trying to achieve a higher output power with a board that isn’t rated for that power? would be interesting to find the cause of this mishap!

[EFR]

Small flashover did make an carbonpath to an pcb top layer, and after that RF skin effekt keeps it burning?

[pukje62]

Can you post picture from open driver box ???

[teckniqs]

Can you post picture from open driver box ???

I've got one here so here you go....

J-Driver-2009-1.png

J-Driver-2009-2.png

[pukje62]

Aha thanks, i see a header connector are these pins connected to the PIC ?? (special pins 12 and 13 at the PIC ??)

[Frequent Lee]

Can you post picture from open driver box ???

I've got one here so here you go....

J-Driver-2009-1.png

J-Driver-2009-2.png

It's not that revision in the box he's posted. It's the earlier one with a 12c508 pic chip.

[teckniqs]

It's not that revision in the box he's posted. It's the earlier one with a 12c508 pic chip.

[radium98]

seems to me blf244 and sd1477 ? or am i wrong .
Is the white trimpot 10k or 1k?

[teckniqs]

seems to me blf244 and sd1477 ? or am i wrong .

SD1407 (designed for HF band up to 30MHz but work great on FM Band II with a lot more drive)

[teckniqs]

seems to me blf244 and sd1477 ? or am i wrong .

SD1407 - designed for HF band up to 30MHz but work great on FM Band II with a lot more drive. There is also a version designed for FM broadcast band SD1460

[Albert H]

Wow! That PA's a "blast from the past"! Back in the mid-80s, when I ran out of the ridiculously cheap aircraft transistors I was using for my PAs, I tried exactly that line-up of the '244 into the '1407, because I had lots of them. Roger H visited one evening to beg some driver transistors from me, and saw the first PCB version of that board. He bought one from me, because (he said) he "needed to get a rig together quickly". Two months later, those PAs started turning up in his rigs....

I abandoned the design, because it became expensive to make, and wasn't particularly efficient. I moved to using the TRW TP93XX devices - loads of gain, and really robust! Shortly afterwards, the first of the Motorola FETs became available (MRF150) and Thomson CSF started their FET series (I favoured the SRF1616). At that point, I could do away with a stage - the gain of the FETs meant that 2 - 5 Watts of drive would be enough for 300 - 500 Watts output!

[Maximus]

Did you get struck by lightning lol

Ooops...

Jel burned out 1.jpg

Jel burned out 2.jpg

Did you get struck by lightning lol

[teckniqs]

Did you get struck by lightning lol

Ooops...

Jel burned out 1.jpg

Jel burned out 2.jpg

Did you get struck by lightning lol

i am not 100% sure what happened as it was only given to me in a rig to take a look about 10 years ago or so but wasn't mine.