PCS-Electronics

Hi, I have an old MaxPro1 unit with lcd display, the output transistor failed (burned) so I replaced it with the same c1971 but now I only get 3.5 watts of output instead of 7 watts. that's about half the power I was getting before with 14.1 volts.
Some thing else could have been damaged in the output?

I lost the manual and circuit diagram, I hope you could please send it to me so I can check it better.

Thanks.

Luis

Send me an email and I'll attach the manual in reply.

How to contact us:
http://www.pcs-electronics.com/phpBB2/v ... 0871#10871

E-mailed, enjoy.

Thanks for the manual Marko..

I checked the MaxPro1 and everything seems to be ok.
As manual indicates for increase the output power, I put a capacitor (12pf is what i found) in parallel to c19 capacitor, with that mod I could get 4 watts on 94.9 mhz, was fine, but thats only a little more output power, not the 6-7 watts like before.

Could be the C1971 transistor a little faulty??
Could it be damaged when it was replaced and now not working properly?

pd. is safe the mod with the 12pf capacitor for the C1971 and BFR96 transistors?

AFAIK the C1971 is no longer manufactured, so most likely you got a used one which may be partly damaged or you got one of those Chinese clones that doesn't work as well. I've read they were doing this with the RD15HVF1 as well. Maybe you could try replacing it with a legitimate RD15HVF1 which I think is still being manufactured? You'd probably need a better heatsink.

The reason I know this is because I blew a lot of money on greek and chinese transmitters before I found PCS and I blew a few transistors. A few of the times they just inexplicably didn't work as well after.

I am actually having a somewhat similar problem right now and I feel bad for Marko because I think he gets these questions a lot and has no idea.

Hi, tnx for the reply,
I got this c1971 since about 10 years (bought it in case of replacement on an electronic local store), but you're right, maybe is not an original.
Now, where to buy original ones?, most online are from china.

about the RD15HVF1, that's a 15watt transistor I think, don't know if it's safe for the MaxPro1, or maybe just not powering full output and less voltage could work fine.

I've already adapted an extra heatsink.

Hi,

RD15HVF1 is a fet so you'd need to perform a number of mods to make it work. I don't think its worth the effort.
2SC1971 is a bipolar transistor.

Guys, these MAXPRO-1 units are really old and obsolete now, consider MAXPRO2015, its low cost and gives you true 15W across entire FM band without any retuning, no fiddling with trimmers necessary at all.

By the time you've fount those old obsolete replacement transistors, if they are original, and replaced them, fiddled with mods trying to get them to work etc you'll spend more time and money than a new 2015+ costs.

And anyone who can prove that he has MAXPRO-1 will receive 10 euro special discount.
This is the code:
10eurformax1

This is only valid to purchase MAXPRO 2015, 3000 or 6015,6025 and 6050.

Marko