M57713 144-148mHz module

[murphyv310]

Hi
I've recently landed another two FT-480R 2 meter multimode transceivers. One had a faulty PLL board and the other not only a faulty PLL board but also a kaput PA module.
I also have another with a dud PA module. After a lot of thought I ordered one from China and it arrived yesterday, so I duly fitted it with no output whatever, the drive is spot on as are the voltages. So I carefully lifted the leg to the first stage and bias and noted there is no current drawn whatsoever, makes me think there is actually nothing in the chip, probably a lump of epoxy.
I've requested a refund....... Will see!

[Cruisin Marine]

To help others, what device was it "meant" to be?

[G6Tanuki]

Those Mitsubishi modules have been unavailable from reputable sources for the last couple of decades. I really doubt that someone in Shenzen province has discovered a warehouse full of new-old-stock ones !

[murphyv310]

Originally Posted by Cruisin Marine

To help others, what device was it "meant" to be?

Sorry, I don't understand the question. The heading is the device that is used in the Yaesu FT-480R. Also the type ordered.

[murphyv310]

Originally Posted by G6Tanuki

Those Mitsubishi modules have been unavailable from reputable sources for the last couple of decades. I really doubt that someone in Shenzen province has discovered a warehouse full of new-old-stock ones !

Indeed I agree, I sat in the fence for some time before taking the plunge and then drowning

[SiriusHardware]

When these modules or similar ones have been discussed in the past someone pointed out that a crack in the 'base' material is a common failure mode and they can sometimes be 'fixed' by joining any broken connections across the crack. Apologies if these aren't the ones in question.

[murphyv310]

Hi.
Certainly the two that are faulty here don't seem to have any signs of cracks. They also don't appear to be soldered with normal solder and even cranking up my solder station to maximum won't melt the "solder" used, one reason I gave up on the old faulty ones.

[Jon_G4MDC]

Some have reported success at stealing these, or the near equivalents, from scrap PMR sets.

It's also the case that repairs can be made to them but you will need a special bench to heat the ceramic/copper substrate to 150-200C or so before you start. Then you might solder normal joints on top with an Iron.

If the bond wires have gone to the semi chips themselves then I expect you are busted. You can only fix cracks in the matching networks between them.

[Radio Wrangler]

The one in the FT480 is a linear one intended for SSB, so its likely to be somewhat different to the PMR ones in biassing as well as tuning.

Plan B would be to turn the set into a QRPp one with output bypassing the PA module, for use with an external power amplifier - using discrete transistors, of course.

David

[Jon_G4MDC]

I long thought that. But then I reckoned not.
They have bias pins for driver and PA stages. Not saying I am right, but I think they just used them as required.

First stage pretty much Class A, 2nd Stage Class AB if SSB or Class C if just FM.

[murphyv310]

Originally Posted by Radio Wrangler

The one in the FT480 is a linear one intended for SSB, so its likely to be somewhat different to the PMR ones in biassing as well as tuning.

Plan B would be to turn the set into a QRPp one with output bypassing the PA module, for use with an external power amplifier - using discrete transistors, of course.

David

Done that with one David
It gives 3 watts and drives a 30 watt linear fine

[murphyv310]

Hi.
The driver transistor gives 250mw at 50ohms and I've directly connected it to the output connection that went to the PA module. Had some reasonable reports on FM & SSB using the radio that way. Adding a 2SC1972 as a PA and biassing it suitably you get around 3 Watts on SSB plenty enough to drive a 30watt Linear amp, even with 3 Watts with a decent antenna I get up to 20 miles on FM.

[Wendymott]

Hi Peeps. I bought one of these modules on Ebay.. and I put it away for "stock" until a suitable project was in the pipeline. I always search for the data sheet and found it easily. Its attached here. I have not tested mine yet, but did a resistivity test between all pins, and apart from the capacitive input and outputs, all seem ok. As I have a clear bench, I will cobble up something to test. Watch this space.