That sounds like some excelent advice. I'm an old NAVY trained Aviation
Electronics Tech Radio Communications been repairing radios for almost 50
yrs I've had a lot of radios over the years That I managed to keep
working A couple years ago I stopped at the TenTec factory an was really
impressed with their line of radios. They are made like a Mercedes simple
,reliable, good engineering, and most of all repairable. I have several
older TT radios that enjoy in my retirement. Feels good knowing that I
got a shot at fixing them RS parts. HiHi Enough of my rambling just had to
throw in my 2 cents worth. 73 KD8BTQ rALPH
On Thu, Nov 6, 2014 at 5:23 PM, Stuart Rohre <rohre@arlut.utexas.edu> wrote:
> NTE and other cross reference general replacement semiconductor companies
> should have crosses to the MPS devices. Don't overlook Mouser,
> distributor. They have vast stocks and fast service at reasonable prices.
> There are still surplus electronics places like Electronic Goldmine that
> often have out of production items.
>
> Substituting bipolar transistors really comes down to getting the right
> polarity, NPN or PNP and other major parameters. A current rating and
> voltage rating close to the original, and frequency cutoff similar to the
> original, or higher than the application you are replacing. Get the Beta
> as close as you can, but remember, there are wide ranges of beta that can
> do the job. The mixer may not be a high gain stage, due to its intended
> function. Most cases of abnormal noise would not be in the active devices,
> (transistors) but in connections, or in faulty passive components,
> resistors, capacitors, and other such components.
> A rebuilt mixer board that is close to the original, is better than a non
> working mixer in a radio just sitting on a shelf.
>
> Don't overlook loose plug in connections from the board to the
> motherboard. Sometimes connectors may wear to cause intermittent noise.
>
> The wiggle test helps here. If wiggling something causes a noise, look
> closely at what moved. Don't be too agressive, but the more experience you
> get with troubleshooting, the better your "touch" will be at finding
> causes of small problems.
>
> -Stuart
> K5KVH
>
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