Kenwood R-5000 Erratic Behavior

[Dominic1967]

I've gotten great help here before, so I wanted to share an issue I'm having with another Kenwood R-5000 I acquired recently. I posted this in the R-5000 group over on IO, as well.

The radio will play perfectly for the first 30 minutes of each day. I suspect once it warms up is when the trouble starts. I assumed the problem might lie in the power supply board, so I swapped it tonight with an eBay replacement. The problem did not go away, so it's somewhere else in the receiver.

I have not tried powering it via the DC connection, but as I replaced the entire PS board, I don't think that will make a difference. If the issue is heat-related, the DC route may simply buy more time, not fix the issue.

I have performed the reset several times (in the video, you see me mistakenly hit the A/B key on power up, instead of the A=B.)

If anyone has ideas on where next to troubleshoot, I'd love to hear them.

Thanks,
Dominic

 

[AB5ID]

Have you tried replacing VL1220/ML1220 on control board? The ML1220 is a widely available equivalent to the original VL1220.

 

[Dominic1967]

Have you tried replacing VL1220/ML1220 on control board? The ML1220 is a widely available equivalent to the original VL1220.

I have not. I did buy a couple of VL2020 batteries to have on hand. I've read elsewhere these were the ones to use.

I have seen in other threads that changing that battery is often indicated with radios that have the PLL unlock issue, but I don't understand the connection. Isn't the battery just for clock and memory?

And speaking of PLL unlock, is that what I'm seeing here? I didn't think that would affect the power button.

Thanks,
Dominic

 

[phask]

I've gotten great help here before, so I wanted to share an issue I'm having with another Kenwood R-5000 I acquired recently. I posted this in the R-5000 group over on IO, as well.

The radio will play perfectly for the first 30 minutes of each day. I suspect once it warms up is when the trouble starts. I assumed the problem might lie in the power supply board, so I swapped it tonight with an eBay replacement. The problem did not go away, so it's somewhere else in the receiver.

I have not tried powering it via the DC connection, but as I replaced the entire PS board, I don't think that will make a difference. If the issue is heat-related, the DC route may simply buy more time, not fix the issue.

I have performed the reset several times (in the video, you see me mistakenly hit the A/B key on power up, instead of the A=B.)

If anyone has ideas on where next to troubleshoot, I'd love to hear them.

Thanks,
Dominic

Never saw that - does the display go black? That is what happens with the PLL issue. It used to start like that, then after an hour or more work fine.
Have you tried leaving it on for an extended time and see if anything happens?

 

[Dominic1967]

Never saw that - does the display go black? That is what happens with the PLL issue. It used to start like that, then after an hour or more work fine.
Have you tried leaving it on for an extended time and see if anything happens?

I haven't tried leaving it on. It works fine immediately upon starting up, then after 30 minutes or so, even without touching it, it goes nuts. After that, even after cooling off for 30 minutes, it quickly goes sideways.

I assumed if it was the PLL issue, it would at least let me turn it off, but no controls respond at all. Reception remains fine, oddly. The screen never goes black and I don't get dots.

Coincidentally, the receiver you sent is arriving today after several weather delays. I'm hoping a recap might resolve any issues it has.

-Dominic

 

[kc2asb]

At first I thought this was the infamous "dots" issue, related to the potting compound around the VCO. But that issue involves all of the digits on the display disappearing.

Subscribing to see what the eventual solution is. Good luck!

 

[phask]

At first I thought this was the infamous "dots" issue, related to the potting compound around the VCO. But that issue involves all of the digits on the display disappearing.

Subscribing to see what the eventual solution is. Good luck!

That's what mine did - the one Dom is getting. Strangley , when I tried after sitting for 10 years,it lit up and worked right away.

 

[phask]

I haven't tried leaving it on. It works fine immediately upon starting up, then after 30 minutes or so, even without touching it, it goes nuts. After that, even after cooling off for 30 minutes, it quickly goes sideways.

I assumed if it was the PLL issue, it would at least let me turn it off, but no controls respond at all. Reception remains fine, oddly. The screen never goes black and I don't get dots.

Coincidentally, the receiver you sent is arriving today after several weather delays. I'm hoping a recap might resolve any issues it has.

-Dominic

If you don't have a repair manual, you soon will...

 

[Dominic1967]

Paul, yours came in today- was waiting for me when I got home. I haven't turned it on yet but opened the box and was pleasantly surprised by the wealth of paperwork and manuals. Thank you so much.

So now I have two units with issues, possibly related, possibly not. But this gives me parts to swap and troubleshoot with.

With the hardened glue in the PLL section, if a test shows it isn't conductive, am I all set or should I still remove it? Is the white or clear glue as problematic as the older brown stuff, or all they all equally bad? Is using a heat gun to soften it going to help or cause a bigger mess?

-Dominic

 

[Dominic1967]

Okay Paul, I don't want to jinx anything but I replaced the big 15000 mF cap in the power supply of the radio you sold me and it's been on for over 2 hours now with no problems. Original was rated at 25V and the replacement, which is slightly larger physically, is 50V.

What issues did it have again?

As for the erratic receiver that's the subject of this post, I went ahead and replaced that same cap too, but will wait until tomorrow to see if it makes any difference. I just love any opportunity to use my new desoldering gun.

Thanks,
Dominic

 

[Dominic1967]

Replacing the cap in the erratic unit made no difference. Same problem- after 30 minutes of working flawlessly, the screen goes haywire and I lose all functionality. It can just be sitting there unattended and it happens. So now I need to figure out which board or component is being adversely affected by the heat. I have other R-5000 units that I can swap parts with and try to troubleshoot a bit at a time. I thought about the head unit first, where the control board lies. or the PLL unit.

-Dominic

 

[Dominic1967]

The battery on the erratic receiver measured 0.68V, so I replaced it. New rechargeable VL2020 battery measures 2.97V out of the package. Nothing changed- 45 minutes after warming up, it goes goofy again. Crazy screen and no control whatsoever. Can't even power it off. While it's still warm, after a reset it still gets scrambled after a few seconds. The heat is doing it. Will start swapping parts one by one tonight.

-Dominic

 

[Dominic1967]

It's not the PLL unit.

I swapped it into a known good R-5000 and the behavior stayed the same- erratic receiver stayed erratic. Known good one stayed good. It's gotta be the control board.

So now I can either buy a replacement control board from Randy at bigapple59 or just say screw it and sell this receiver for parts. I just don't look forward to replacing it. I started disassembling it tonight and thought it was too much of a hassle but then I remembered I replaced a display unit on one maybe a year ago. Got it from Randy. I was really proud of myself and posted about it. So I must have had to disassemble all of this before.

-Dominic

 

[AB5ID]

Have you tried an external power, monitoring the regulated supply voltages, running with the cover off with a fan, or freeze spray?

 

[Dominic1967]

Have you tried an external power, monitoring the regulated supply voltages, running with the cover off with a fan, or freeze spray?

None of those ideas, yet. I do need to get some freeze spray, just to have it on hand. I'll hook up the DCK-2 kit tomorrow and see if that makes any difference.

-Dominic

 

[Dominic1967]

I fixed it.

Long story short (and it's a funny story) I completely disassembled the receiver to clean... wait for it... pee that had gotten in via the AC port and worked itself into the crevices along the rear heatsink that the rectifier and voltage regulator transistor attach to. Ugh.

I removed everything down to the chassis and cleaned the metal with 99 percent isopropyl and scotch brite pads. I ordered a replacement transformer assembly complete with rectifier and such, applied thermal paste (and arctic silver to the more important parts) and put it all back together.

Plugged it into the dim bulb tester and powered it on. It's been on for two hours with no issues and I swear it's running cooler, though I don't see how. So, that's it- I'm emotionally spent but very relieved. It seems to not suffer from key bounce as well, so I may swap IF boards with another unit that has all filter options filled and keep it as my main unit.

This was a really fun project.

Thanks,
Dominic

 

[MTS2000des]

Cat piss has killed more electronics than rodents.

 

[Dominic1967]

Cat piss has killed more electronics than rodents.

And now you can add Racoon to the list.

 

[AB5ID]

Good Job! Thanks for sharing.

 

[Dominic1967]

Good Job! Thanks for sharing.

Thanks. Just noticed your location- I managed a Borders in Lees Summit for a short while. A life detour had me living in Olathe, KS for less than a year. Nice, but flat. Very flat.