ICOM IC-2410H - 1991 Ham Radio rebuild - sorta

[B1nary]

There are a bunch of new amateur operators just getting their basic class license and don't have a lot of $$ to spend on a dual band radio. Since I have a few older ones I can fix and give away to those who can't afford a new one, I recapped and did an alignment on the first one - well I tried. It is a IC-2410H. The VHF side has improved dramatically. But I have a real headache with the UHF side. I can change to any of the UHF frequencies using the front panel knob, the memories are fully functional storing offsets, T/Sq settings, DTMF tones etc. I can switch bands between VHF and UHF and open and close the squelch manually. In fact it seems everything is working as you would expect except there is no transmit and no receive. I've checked the PLL/VCO voltage for UHF side and while it is supposed to be 5.5V I only get 3.2V. There is an adjustment for this on the top side of the board but this adjustment does not make any difference. I checked the supply line going to the PLL and it shows 5.6V- close enough for me. Does this sound like a problem in the PLL/VCO itself.  To make matters worse (as if they are not bad enough) this is my first foray into ham radio repair. It just seems like I am missing something so obvious but don't know what it is.

Any help, direction or things I should check will be appreciated (and help me get a radio to someone who could use one).

I've attached the schematic for this section of the radio.

[oldmannewstuff]

Hello!

Sorry I can't help you with this one, but have you watched the "TRX Bench" channel from Youtube? Tons of detailly explained videos on repairing ham equipment 

[B1nary]

Thanks for replying and yes I do subscribe to his channel. One problem is that he asks that you don't send in personal  questions so that eliminates him as a resource.

Somehow it feels like I am missing something really simple and I'm going to feel like an idiot when it comes to light.

If anyone else is reading this, I am open to suggestion . . . anyone ....?

[imidis]

I can't be of much help, but I know w2aew (on the forum and youtube) has done ICOM repairs maybe he can give you some pointers.

[oldmannewstuff]

Just a thought, but have you checked all diodes, coils and resistors with a multimeter?
No absolute need to check coil inductance, just continuity would suffice at this point. I once had a SMPS with coil that looked ok on the surface, but had burned on the inside. 

[B1nary]

Shots of the front and back side of the board. You may notice a couple of trace issues where, because of how many times I removed this board, the trace has lifted in part. I can assure you that I have repaired the trace and have full continuity through the connection to adjoining components. Also FWIW all the caps in the radio have been swapped out for new ones. I did check each cap for ESR before putting it in but I did not check each for leakage.

I hope this help someone point me in the right direction.

[B1nary]

No I haven't. Part of the reason is that my apparently flawed logic keeps pointing me back to the very low PLL/VCO voltage on the UHF board (3.2V vs 5.5V) that I can't adjust upwards. The supply voltage coming to the PLL/VCO is correct and by all right adjusting the coil inside the PLL/VCO, I should?? be able to increase the voltage but no matter where I adjust that coil, nothing happens. The 3.2V reading just stays the same. If my assumption is wrong can someone let me know (if the voltage to the PLL/VCO is too low (I think 2 volts low would be considered too low) than there is no way for the PLL/VCO to lock up. If I don't get lock up I don't think the radio can either receive or transmit. If I am wrong (not an unusual occurrence lately), then I need to look for the problem elsewhere. In case you are just joining this post, the VHF side of the radio is fully functional and in fact it's output power meets and exceeds the specs stated for the radio.  The UHF side does everything it should in terms of memory allocation and recall, offset settings, tone squelch, power output adjustment, and manually opening and closing the squelch (so the receiver is not totally dead I do get speaker hiss), but feeding it a UHF signal does nothing and nor does keying up the mic (which works on VHF) does nothing.

[B1nary]

If anyone is still reading this  . . . I have downloaded all of the IC-2410H Service Manuals that I can find. The scan of text in them is decent but when it comes to the board layout of the components none of them are fine enough to make out the name/number of the parts. Even if I find one that allows me to locate a specific part on the board there does not appear to be any test points I can access to test for a signal. I can access the top side connectors and measure voltages but after that even trying to use the ever present VIA's I can't get any readings. ICOM use to have trouble shooting procedures for this radio but of course they no longer have them. The major problem is that you do not have access to any of the "bottom" side of the board because of the direct connection to the front panel of the radio and the multi pin connectors from the front to the top and bottom PCB boards. I am guessing that when these radio were current there was some type of cable/connector layout that was employed to gain access to the bottom side of the boards for troubleshooting purposes. This is pure speculation on my part. If anyone has ever worked on an ICOM IC-2410H OR a IC-3220H, would you mind telling me ow you managed to service these things without gaining access to the actual bottom side component layout.  As it stands without a component location layout and a method of testing I am stumped at how to proceed.

Anyone anywhere  . . .?

[CJay]

Still reading, in fact just found the topic.

Stop twiddling.

Something doesn't smell right here, there are two VCOs and two PLL units in this radio, both capable of running VHF-UHF so there's something very not right going on here.

Are you certain you're on the right VCO, have you set both A and B to a UHF frequency and tried to TX on both?

I'll print the schematics on Monday as I've got a large format printer there so I can follow them properly but check the obvious things, have both PLLs got a reference clock, is the DC-DC converter running, it should produce 30V and you can check that on J3?

If that 30V is 'wrong' then the VCOs will not have the range they're meant to have.

[B1nary]

Thank you for helping out! The VHF side of the radio Xmits and receives great. While I am new to electronics (just so you know) - I want to fix these radios to give to young just licensed amateurs and learn something in the process. To answer your questions. J3 has 33.4V. The only way I found to set UHF on the A Band or VHF on the B band was to enable a function called PARA Watch (Hold the band switch in while applying power). Then I can set a UHF frequency on the VHF side. In any case I have the 33.4 V noted above on the J3 connector.  According to the User Manual you cannot transmit the second frequency while in Para Watch mode so when I set a UHF frequency on the VHF side and try to Xmit the radio shows OFF - which the manual says is normal. When I set a VHF frequency on the UHF side and try to Xmit it also shows Off - also normal. Having both displays showing 445MHz and feeding a 445MHz modulated signal to the radio; I can hear the modulated signal in the speaker. While receiving the 445MHz signal the S meter on the VHF side of the display works fine but I don't get any meter reading on the UHF side. When I switch to the UHF side of the radio still set to 445MHz and key up there is no transmit and of course switching to the VHF side of the radio and keying up shows Off - normal.

Setting 145MHz on both displays with the band switch set to the VHF side I can Xmit and receive just fine. However if I set say 142MHz on the UHF side and feed a modulated signal to the radio -  there is no receive.

I hope I've explained this so it makes sense and apologies if I haven't. I'll try whatever you suggest since nothing I've tried has worked.

[bob225]

its all in the service manual page 36 on gives you the test points and calibration info, further in the manual are the board layouts and component locations

25 mb manual

https://www.palomararc.org/Manuals/IC-2410_service_manual.pdf (right click save as)

[B1nary]

I previously downloaded several manuals from various sites across the web. The problem is when you expand them enough to see the component names/designation on the board layout, the print is out of focus, including the link you kindly included in your message. I thought it might be a monitor problem but I am running a 1920 monitor and am not sure buying a 4K monitor would resolve the focus issue if the scanned resolution of the service manual was low to start with. And as if this isn't frustrating enough, when I tried to sign in to reply I got an error message saying my session had timed out. So, 4 browsers installs later, I am forced to use Chrome (not my favourite), but at least I can sign into the forum.

Thanks for your help.

[bob225]

All of them are like that, tell me what pages you want and I will see if I can sharpen them up, I can read them ok-ish if I take off my glasses off

I have adobe photoshop and acrobat DC Pro so should be able to do something

[B1nary]

All of them are like that, tell me what pages you want and I will see if I can sharpen them up, I can read them ok-ish if I take off my glasses off

I have adobe photoshop and acrobat DC Pro so should be able to do something

The pages that would help are the Main A Board (top and bottom layouts) and the Main B Board - top and bottom layouts - and if you are successful - the Main B Board VCO/PLL component lay out board as well.

I really appreciate you taking a look at this.

[bob225]

I run it through DC pro, enhanced it a bit changed a few other things about - is still not great, ideally it needs going through page by page and touching up manually

see what you think

https://www.dropbox.com/s/hf5blyup5u7u62c/pcb%20IC-2410_service_manual.pdf?dl=0

[B1nary]

Your copy is certainly far better than anything I have. You are correct it does still need a touch up to read clearly. I am still going to try to follow it - I don't see many other choices at this point. Trying to enhance these old manuals reminds me of trying to make an out of focus picture - in focus. It just never seems to work. If I wasn't so new at this and so stubborn I would have tossed the radio a long time ago.

Anyway, back to my favorite sport - 

[B1nary]

Thank you for helping out! The VHF side of the radio Xmits and receives great. While I am new to electronics (just so you know) - I want to fix these radios to give to young just licensed amateurs and learn something in the process. To answer your questions. J3 has 33.4V. The only way I found to set UHF on the A Band or VHF on the B band was to enable a function called PARA Watch (Hold the band switch in while applying power). Then I can set a UHF frequency on the VHF side. In any case I have the 33.4 V noted above on the J3 connector.  According to the User Manual you cannot transmit the second frequency while in Para Watch mode so when I set a UHF frequency on the VHF side and try to Xmit the radio shows OFF - which the manual says is normal. When I set a VHF frequency on the UHF side and try to Xmit it also shows Off - also normal. Having both displays showing 445MHz and feeding a 445MHz modulated signal to the radio; I can hear the modulated signal in the speaker. While receiving the 445MHz signal the S meter on the VHF side of the display works fine but I don't get any meter reading on the UHF side. When I switch to the UHF side of the radio still set to 445MHz and key up there is no transmit and of course switching to the VHF side of the radio and keying up shows Off - normal.

Setting 145MHz on both displays with the band switch set to the VHF side I can Xmit and receive just fine. However if I set say 142MHz on the UHF side and feed a modulated signal to the radio -  there is no receive.

I hope I've explained this so it makes sense and apologies if I haven't. I'll try whatever you suggest since nothing I've tried has worked.

Just an update in case you are still around. I decided I would go through the Alignment process for the radio and see where things are wrong and try to make a list of them. Well I didn't get very far (step 2 actually). One of the settings for VHF lock voltage is to set 145MHz on the UHF side and measure the voltage at CP1. The reading should be 5.5V. Well . .  . it is 22.94V! and trying to adjust the B-Side Board VCO voltage to 5.5V isn't possible. It will move down to 22.4 but that's it. Now I suspect a problem within the VCO itself and if my guess is correct, getting that thing out is a big deal. Are you aware of a process to trouble shoot the VCO without having access to the bottom of the B-Side Board.

[B1nary]

Information Needed.
If you worked as an ICOM Tech back in the 1990's onward (or have the answer to the following question), I would appreciate your input.
I've finally sourced a readable board layout for the IC-2410 I am trying to restore. As you may know these radios were built with a solid aluminum chassis piece separating the VHF Board from the UHF Board and both these boards were attached to the front panel with a multi - pin connector (one for each board).

What I would appreciate knowing is how you tested the radio with no obvious test points on the top side board (either VHF or UHV)? Short of building a jig of some sort to connect both boards to the front panel connector allowing me lift the boards to gain access to the bottom of the boards, I don't see any obvious way of doing a trace for signals from the top of the boards.  If you've read this post you will know I am new to this so the obvious to you won't be for me, so any help is appreciated.

TIA