AM filter replacement for R71A
If you have the info could you pass along what was the AM filter you replaced in the R71A.
As you know the R71A lacks in Hi Fidelity audio. I assume your using something slightly
wider than the stock 6KHz filter.
Thanks,
Ken
N1KK
The R71's are fun radios.
I did change the AM filter for one that gave me a much cleaner sounding audio for the AM broadcast band. I think that was about the only thing I did not like when I bought it. AM broadcast was 'muddy' sounding too my ears.
SSB and other mode reception was great though.
I do have other radios that have more control over filters and many other options but I always go back to using the R71A.
I wish I still had the Mouser info but that has been years ago now.
I'd found a nice yellower color extra wide angle LED that worked fantastic in my R7000, R71A and even my R9000 plus the dimmer worked evenly with the other control lighting in the R9000 and the ELD display's in the R7000 and R71A.
I had to add a decent high ohm resistor to drop the voltage enough for the LED but it was an easy calculation.
My first attempt used an LED that was more of a 'spot' beam an resulted in a bright spot in the center of the meter. I finally found a model shaped more like a T4 or T3 size LED that even fit the rubber grommet well. It had a much wider output and lit the entire meter very evenly and nice an bright but not overly bright.
I don't run my R7000 or R71A in the High brightness position as I don't know if the vacuum type LED display lighting used in those radios fails over time and I know finding a new display would be next to impossible so I usually run the lighting on low. My radio bench is dark anyway so low works out about perfect.
The R9000 uses all LED lighting from the factory except the CRT and the S-Meter backlight which I'd changed to LED from the day I bought it.
I also have several spare CRT's in case that fails but mine has not burned an image into it and can still be turned up very bright independently from the other lighting. I keep saying I'm going to swap out the CRT with an small LCD panel but never have. I always figured I can use an external CRT if the internal ever fails along with all my spares.
An wide angle warm white color temp LED works very well in the R71A though if you ever get around to changing it out.
Even if I did have the original Mouser part number, chances are good that they no longer sell that model anyway but they do have tons to chose from. Maybe someone that has done one of those model receivers recently will chime in with a modern part number.
It's probably the easiest part to change in the entire radio!
Did you swap out the ram board with a non-volatile model so you don't loose the OS memory if the coin cell backup fails?
The R71A has that problem but the R7000 used a different board that did not have that problem if you ever purchase the matching R7000 to go along with your R71A!
I re-capped both of mine some time back and they work like new although digital signals have really slowed down my use of the R7000.
It's still fun to turn a large and real tuning knob though! I use the R7000 mainly for rail and air monitoring and then general tuning when looking for new digital signals.
I also have the remote control for my R7000 which is fun.
I moved the only speech board I had into the R71A but never did add the computer control into the R71A as it looked complicated compared to the CI-V TTL interface used in all the other models.
The R71's are fun radios.
I did change the AM filter for one that gave me a much cleaner sounding audio for the AM broadcast band. I think that was about the only thing I did not like when I bought it. AM broadcast was 'muddy' sounding too my ears.
SSB and other mode reception was great though.
I do have other radios that have more control over filters and many other options but I always go back to using the R71A.
Glad you figured out the problem and were able to get it all going!
It should give you several years of enjoyment!
Swap that ram board though if that has not been done yet. It's an easy swap but most require two solder pads be soldered together for the model radio it is going in. The new boards also give you an extended tuning range. Some of the new range is not useable or is but with reduced sensitivity. Some ram boards still use a coin cell but it only backs up the memory channels while the small area used for the OS is now in a non-volatile section of the boards eeprom.
Almost a plug and play board except for the solder pads that must be soldered together so the board knows what radio it is going into.
If that has not been done in yours, several sell them but a company name PIEXX comes to mind. I think they sold several accessories for that era radio.
And as I think you found out, one must be careful when working inside as the wiring was mostly external between the boards and was/is fragile!
Luckily you can find nice quality PDF versions of the service manual though. I took close up pictures of mine before I dug into the insides. Those came in handy when a wire would break!
Then the fact that most of the radio's from that era used standard thru hole components really helps should something fail. Almost everything in that radio can be replace with components still readily found today.
Maybe the processor and display logic components would be impossible to find but most of the other items can be found including RF/IF components even if you need to 'roll your own'.
Can's and coils can usually be salvaged from other old radios and even chips used in the IF stage can usually be found as well.
I can't recall any sudden failures of things like the processor. If it did fail, it was almost always user error by the person attempting repair or a nearby lightning strike.
Have fun with it now that it is up and running!
