Flameout
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Posts posted by Flameout
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I checked the voltage regulator on another 880 and it was basically the same. 13.8 and 7.94. I'm looking over the board now with strong magnification under a bright light.(I will probably need some Tylenol after this)
I took the board out of the case, so the photo is the part that was hidden by the case. Is that white stuff normal or are those components failing or already failed?
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oh wow, ok. I just read through the data sheet again (I may have to read it a few times) I just checked that voltage regulator that I put in. It was showing 13.8v / gnd / 7.88v so pin 2 of the PA is getting that 7.88 from the volt reg so I guess I can start from there, or should it actually be 6v? I guess the 17v is like the maximum?
At least I can hold off on buying a new PA for now. I know I'm probably putting more into this old radio than it is worth, but it's kind of fun trying to figure it out
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49 minutes ago, axorlov said:
Yes, this is the part. I agree with Sshannon, oscilloscope would be needed. But here is the datasheet for the PA, just in case: https://www.mitsubishielectric-mesh.com/products/pdf/ra45h4452m.pdf You can quickly check the voltages on pins 2 and 3 (refer to Page 2 in datasheet). Maybe the PA is fine, but there is no driving voltage. It also may have an effect on the audio amplifier.
Thanks for the link. I'm getting a nice little collection of Kenwood TK-880 files.
I checked pin 2 and 3 and only pin 3 was gettting power, so maybe the PA is good after all. If I were to bypass everything and temporally supply the (13.6) voltage to pin 2 to see if the radio would actually transmit, would that do more harm than good? I guess I'll start tracing back and see if I can find the problem
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Ok, thanks. Well that is well above my pay grade lol. I may take the risk and offer this seller $30. I just have no idea what else may be wrong with the radio. It powers up, programs, red light comes on when transmitting and green comes on for receiving and it is working ok as the rx radio in the repeater setup and sending that signal to the tx radio https://www.ebay.com/itm/403511558565?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=6B03kewjR7i&sssrc=2047675&ssuid=0zihXCkJQWG&widget_ver=artemis&media=COPY
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40 minutes ago, axorlov said:
You have dummy load or proper antenna on the other side of your power meter, right? Right?? If yes, that is a very strong hint that power amplifier is a toast. I'd say 99% probability. The HT nearby receives the very low radiation from the internal low-power traces and wires.
Oh, I did have an antenna connected. I guess the power amplifier is the part that I have circled in my photos? Looks to be around $40 for the 40w, for the 880H. Not sure if it's worth the gamble. Is there a way to test the power amplifier that you (or anyone) know of? I guess that also affects the audio output?
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Are the only differences (besides the obvious larger heat sink of the 880H) on these two radios just the RF MOSFET Amplifier Module and the extra voltage regulator on the 880? Am I missing something else?
I bought a non working 880H and was able to get it to power on by replacing a diode, a capacitor and the one voltage regulator, but there is no audio and no power coming from the antenna, even though it is transmitting and receiving. I started looking at the two and those are the only differences that I see. Seems weird that the lower power 880 has the 2 voltage regulators where the 880H just has the one. Also, any idea why the 880 has no audio and no power coming from the antenna wire (I tried external speaker and had swr?watt meter attached to antenna wire with zero SWR and zero watt output - even though when I transmit, it is being picked up on an ht nearby) Another thing too, even though the display works on the 880H, the LED's don't
Also, don't mind those extra wires. I was testing these radios as RX radios in a portable repeater
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I was getting just over 5.7w from mine, and close to 11 when I checked before it went into the duplexer. I'd be a bit upset with that 2.27
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29 minutes ago, gortex2 said:
Yes if the radio is set for RX/TX on the 462.xxx you can talk and receive on it. The GR series repeaters used to ship with a mic for that reason. It would allow a "dispatcher" to talk back to his vehicles without needing another radio on site.
Could I have that radio set on a repeater channel, say R21, and transmit 467.700 to a repeater and Rx back on 462.700? I didn't explain myself very well in the previous post,sorry. Just didn't want to screw up the duplexer if I were to TX into the low side which is meant for 462.xxx. Maybe I should just get another antenna
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I was able to update the firmware of my nanovna (from 0.4.0 to 0.8.0 build date nov 25, 2019 to jun 19, 2020) so not sure if it's even the latest, now to work on checking the duplexer, but I do have another question.
The two TK-880's that I'm using as my portable repeater, can I still use the Tx radio of the repeater to transmit on? Of course it takes it out of the 'repeater' configuration. For example, I still have it programmed with the GMRS channels, but when using it as a repeater, I have it set on channel 19. Can I just plug a mic into that Tx radio and use it, transmitting while it's still connected to the duplexer? Reason I ask is that it is receiving much better on the antenna connected to the duplexer than a small junk antenna connected to my other GMRS radio. The photo is how I have it set up, and the radio on the right is the Rx radio, which is still programmed to the GMRS channels
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On 8/12/2022 at 10:38 AM, Sshannon said:
The best advice I can give you is to download and use the free software: https://nanovna.com/?page_id=90
I was able to get the software up and running on my laptop (win10) but unfortunately can't get it running on my shack computer (win7) First things first, I need to work on updating my older nanovna. Running version 0.4.0-3-ge04d3af from Nov 25, 2019 and as soon as I can figure that out, I'm going to give it a shot at seeing if I can figure out where this duplexer is tuned. Right now I have it up and running on .650 and seems to be working ok. Can this cause interference on say .625 and .675 if it wasn't specifically tuned for .650?
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Thanks for that info. There was a video on you tube where someone used that same spectrum analyzer that you linked to. For that price, I may have no choice to to buy one, or something similar haha. The ebay link was also showing a few others. I initially was just building a portable repeater that I could take camping, use in emergency etc but it's easy to get carried away. Although the repeater was working ok using two antennas, adding the duplexer and going with one antenna I thought would be easier.
So I now have the cheap Fumie duplexer which I didn't have tuned but says 462-467. I was just curious as to what they actually tuned it to.. I haven't tired it yet as I needed two more N connectors. Really appreciate the help and advice from these forums
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55 minutes ago, JeepCrawler98 said:
Can you post a pic of your test setup and change your span to 10mhz centered on 465? The dynamic range on a NanoVNA isn't great but you should be able to see down to -70dB somewhat OK. A notch at -22dB is barely anything and indicates something's amiss.
I'm going to have to learn this VNA a little better first. I'm kind of lost at what you are saying. I bought this thing over a year ago, but never really got the hang of using it
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Ok, thanks. I'm gonna give this another try. I got these numbers but I just had the nanovna connected to low then high. 463.860 and 464.280. It said it was tuned to 462 -467 so I guess I should expect something closer to that
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Is there a way to check a duplexers high and low preset using a nanovna? I realize you can tune one this way, but thought maybe there might be a way to find this info. You tube wasn't much help
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Ok, thanks. I certainly don't have the equipment to tune one of these things. Seems I have (lots) more reading to do. I have no idea if they are br/br or bp/br but one was a Fumie the other I didn't see a name. Both from China of course so certainly not high end duplexers. I just made a portable repeater out of two Kenwood 880's and it's working ok with separate rx and tx antennas but thought it might be easier with just the one antenna.
This isn't something I planned on operating 24/7. Just traveling, camping etc. And I imagine a duplexer would take away some of the power from the TX radio. It's putting out 24 w right now so a duplexer would probably take half of that. Been looking for an 880H, for that little bit more power, but the ones I've found must have gold bars stashed inside
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I'm sure this has been answered, but I can't find it. (Sure are lots of results when searching duplexer)
If a duplexer says it has been tuned for 462-467 does that mean it will now work on all of the GMRS repeater frequencies, or does it need to be tuned for a specific frequency, like 462.650 - 467.650?
I asked a seller on ebay and they had no idea.
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- In my area, GMRS is all but useless during the day. Pretty my nothing but road crews, construction and others and they ALL seem to want to use 15-22 so more repeaters wouldn't even help. Already have repeaters on 600, 625,675,700 and 725 but as I said, no sense even bothering with it till evening
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23 hours ago, TNRonin said:
I figured that all they can do is say no, so I sent them a question if they had any discount codes. I ended up getting the rt97 delivered for $340!! I didn't get the two radios because; 1, I already have plenty, 2, I didn't think to.
I had been gaming the cart thinking that the radios were the reason for that crazy shipping, and I forgot to put them back on. Still happy with the cost. Oh and getting 5-7 days shipping.
Sent from my SM-T860 using Tapatalk
I got about the same deal. $338 and it included the gmrs antenna and the coax. And it only took 4 days from ordering until it was at my door. I'm actually surprised at how well this little unit works
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7 hours ago, Lscott said:
Do you have the service manual for the radios? Manufactures can and do change versions because of hardware design changes. That could apply to the display too. You simply might have a different, electrically, LCD display verses the other radio where they are not compatible. The service manual might show the differences.
No, but I'm sure I'll be able to find it. I'll do some searching now. Thanks
Axorlov, I don't have that firmware file. Reading through the thread, I believe it is E613.zip right? I haven't had any luck finding it. Right now I have that V 2.0 radio set up as a Rx only in a makeshift repeater system that I made using 2 TK880's and so far it has been acting ok. No yyyyy screen, but my email is my username at gmail
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7 hours ago, axorlov said:
When you are talking about swapping the display, are you swapping only the display or the whole front panel? The brains of the TK880 is on this panel. All the settings, calibration, firmware, etc.. The stuff in the big box is mostly the actual radio components, as opposed to electronics/microcontroller components.
Yes, the entire front panel. Just two screws and the ribbon cable. Sorry for not being more specific. I'm kind of surprised that all of that stuff is on that small PC board. Still confusing though. So my 2.0 radio itself is ok, it's the front panel that has the problems. So the radio box is the same between versions, just the display panels are different?
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I realize that this is an older thread, but I've been playing around with a few TK880's (2 are V1 and 1 is V 2.0) I just recently got the V2, programmed it and worked good for a few days, then I got the yyyyyyy screen. Reprogrammed it again and it was good. I noticed the display was brighter than my other 2 radios, so I swapped it to on of the better radios (the V2 was in bad shape, as far as crud on the PC board)
Was an easy swap and all was good, but then the V1 that I put the brighter display in got the yyyyyy screen. I then swapped the screens back and that is when I realized that it wasn't the radio causing it, but it was the display itself and the yyyyy display showed up on the previous good radio and the bad radio that was showing yyyyy was now fine
The V 2.0 radio was also showing VER: 1.5205 but that too follows the screen and nothing to do with the radio as it also was showing that when I had that screen in the other radio. How is that possible?
I still haven't found a way to fix that V 2.0 radio and the yyyyy. When I bought the radio, it was SUPPOSED to be the 880H but seller sent wrong radio so he refunded my money and let me keep the radio. I'd be a little more upset if it was the 880H and I put money out on it. BTW, still looking for an 880H
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The outside antenna is a Comet CA-712 EFC. I kind of just now reconfigured my shack. I'm now using the Icom 2821 for GMRS (and scanning) and back to only 2m-440 (and scanning) for the Icom 2730 with an outside Comet GP-6. I'm still a bit surprised at how much better the older 2821 receives signals
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I found this out by accident while playing around with some radios. Two older radios, an Icom IC-F2821 and a couple of Kenwood TK880's and a newer Icom IC-2730a.
I have been using the 2730a mostly, but stuck a cheap mobile antenna into the 2821 and started picking up a somewhat local GMRS repeater that the 2730a wasn't receiving, using an outside, roof mounted antenna. Tried the cheap mobile antenna on the 880 and also worked great, picking up the repeater. I tried the mobile antenna in the 2730 and nothing. Of course both the 2821 and 880's worked great with the outdoor antenna.
Is it because the 2821 and 880's are more of a commercial radio where the 2730 is more consumer oriented radio?
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2 hours ago, axorlov said:
Not clear to me. You say you unscrewed antenna and stick brazing rod into the center connector of the mount, as a vertical element? How you would do that? NMO mounts do not have a hole to insert a rod.
The top part of the antenna can be removed and it is the exact diameter of brazing rods that I have. They fit right in and can trimmed to achieve a good swr
TK880 vs TK880H
in Technical Discussion
Posted
I did those tests and nothing at all on pin 1, 2, 3 0r 4 when set to Voltage AC. Went back to DC and did the same test. Keying the mic gives 0 on pin 1, 1.7 on pin 2, pin 3 is the 13.8 so no change there, and pin 4 was 1.5. Of course still Zero watts and zero SWR. I'll keep playing around with it. Maybe I'll get lucky