RF-7850M Issues

[mfn002]

I recently acquired an RF-7850M-HH-001 off of eBay. The seller was very clear that the radio had two main issues: 1) No audio from the front speaker and 2) the radio had power issues, which he blamed on a pin on the battery connector that wouldn't extend out all the way. With testing, I discovered that the power issue occurred when the PTT key was pressed (it would power off and then back on again). The audio out of the top connector works fine, although the volume level is a bit low. The built-in microphone on the front of the radio works fine as well.
I mainly got this radio because a 7850M with issues was a lot cheaper than a fully functioning one. I can live with using an external speaker mike and the power issue but would like to know if there is any way I could get this repaired.

Yes, I know this was probably an ill-advised purchase, but my birthday is coming up and I wanted something interesting--even if it did nearly bankrupt me.

 

[redbeard]

I have the 'radio #1' from the same seller/batch (they were listed elsewhere before yours hit eBay) and despite no known or disclosed issues it ended up having an extra screw inside that made it's way down to the battery terminals inside and was shorting out the supply voltage. It's been doing well ever since that screw was removed.

There are what may be a couple fuses on the flex attached to the power connector, perhaps one of them is bad limiting current at TX. I saw a replacement flex+pogos on ebay for sale from China FYI.

Another idea is to try to transmit on different bands and different power levels to see if it's better or worse anywhere. There are many RF modules inside the radio and one of them could be bad causing this.

The radio disassembles easily and it would be worth making sure the speaker didn't just come unplugged inside. It's not the loudest when it does work though.

Software is going to be a pain to get, esp. since mine is on much newer firmware than yours (6.3.1) and if anyone can help let us know. It seems the CPA application also requires extra 'plugins' for many of the waveforms so those are needed too.

You can probably make your own interface cable using this: RF-7800 6 ft. Cable Un-Terminated

 

[mfn002]

I've checked and the speaker is plugged in. I also checked the flex both to the battery connector and the one to the front of the radio and both were fine and seated properly. I'm not too sure what's going on, but I have a nagging feeling that the audio issue has something to do with the circuit board the display, keypad and speaker are connected to. I came to this conclusion because I noticed that I had to press the keys on the keypad very hard to get them to respond and the fact that the external audio output works.

I'm not sure about the power level being the cause of the power issue, because I forgot to mention that it is intermittent and manually switching the radio off and then back on again seems to fix it.

 

[prcguy]

Since these radios do not have type 1 encryption you might be able to get an account with Harris and have it repaired. I know a guy who has done this, however that will probably cost more than you paid for the radio. There is a guy who is pretty good at working on modern mil radios but he's not cheap either.

 

[mfn002]

Do you have any contact info for this person who works on these modern military radios? I might want to do that.

I might want to add that I ran the self-test on the radio and it came back with no errors.

 

[prcguy]

Do you have any contact info for this person who works on these modern military radios? I might want to do that.

I might want to add that I ran the self-test on the radio and it came back with no errors.

That would be Jim K in Michigan, I'll look for his contact info and PM you.

 

[mfn002]

Thanks! I paid north of $2000 for this radio (bidding war), so I'm pretty sure repairing it would cost somewhat less than what I paid for it.

 

[TDR-94]

L3HARRI$ flat rate repair, for the tactical radios, is going to be more than what you paid for the radio.If they even entertain the idea of repairing it for you.Your best bet would probably be taking prcguy's suggestion for attempting repair.

 

[mfn002]

I emailed prcguy's recommendation yesterday and I am still waiting on a response.

 

[mfn002]

I didn't get any response from prcguy's contact. Does anyone know if and how I could get some parts for this radio? I'm mainly looking for the front panel, since I suspect that's where the problem lies.

I did manage to fix the battery contacts by swapping the assembly out with one from an RF-7800T ISR receiver that I had laying around.

 

[TDR-94]

Parts are pretty much going to unobtanium for those radios, other than purchasing another radio for parts and hoping subassemblies aren't serialized between radios or running on different firmware versions.

 

[mfn002]

Parts are pretty much going to unobtanium for those radios, other than purchasing another radio for parts and hoping subassemblies aren't serialized between radios.

That's what I was afraid of. At this point, I guess I should just continue watching eBay and see if any parts come up.

 

[prcguy]

I emailed prcguy's recommendation yesterday and I am still waiting on a response.

I sent the only contact info I had. I will see the guy at Dayton next month.

 

[mfn002]

I just joined a group on groups.io called "HarrisRadio". They seem to be mainly concentrated on Harris RF-series military gear. I added a post on there and I'll keep this thread updated with whatever the response is.

 

[mfn002]

UPDATE:
I found the issue--I hope. The speaker was dead. Thankfully, there was easily removed silicone holding the speaker in place, so I pried the speaker out and ordered a (similar) replacement on Amazon. I just don't understand how the speaker could be dead considering that the radio is in almost mint condition.

 

[prcguy]

The bad speaker is probably the reason you now have it.

 

[mfn002]

Correct. I'm surprised that the military didn't try to fix it.

 

[prcguy]

Correct. I'm surprised that the military didn't try to fix it.

They don't. If its under warranty I would expect them to return it to Harris but if not its headed for surplus disposal. If it had Type 1 crypto you would probably not have it without the US Gubment making some of their typical mistakes.

 

[mfn002]

I saw some date stamps on some of the frame components that indicated that they were manufactured in 2013 or 2014.

 

[mfn002]

Oh, and another thing: What's the difference between Falcon II and Falcon III radios?