Faulty Yaesu FT726R

PaulR

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Bit of a long shot on this but here goes...

I bought a Yaesu FT726R as a non-runner/unknown quantity a year or two ago at an SK sale from a friend's brother. He had no personal knowledge of it at all and all it came with was a photocopied operating manual.

Yesterday I dug it out and thought I would have a play with it. First thing was to make a blanking plug for the 12V loop-through and then I powered it up. No variable transformer I'm afraid so it was just straight mains. It lit up but only had an 'E' on the display. The operating manual helpfully says this means error.

Just in case the internal PSU was faulty, today I used an external 12V supply set at 13.8V. No change, still the 'E' on the display. The external PSU meter says it's taking about 1.5A, which is correct by the manual.

So... has anyone come across this before? Any idea of how I should approach investigation?

All the repair shops (none of which are close to me any way) are closed at the moment but it may not be an economic repair if push came to shove.
 

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1983 ?

Every other site says 'psu capacitors'
 

Terryl

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Check the position of the backup switch,(top cover of the unit) if it's in the on position then the internal memory backup battery may be dead,(unit was powered down too long) you may need to replace the battery.

If this is not the case then the controller PCB may need to be replaced, or the caps need to be checked.
 

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Apologies for the adverts

 

Terryl

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I would also check all the wired/plugs connections, the connectors may need a bit of a wiggle to connect.
 

PaulR

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[/QUOTE]
Yes, exactly that one (well actually a better copy than that version).

1983 ?

Every other site says 'psu capacitors'
I thought that as well but it's the same problem when fed from an external power supply.

Check the position of the backup switch,(top cover of the unit) if it's in the on position then the internal memory backup battery may be dead,(unit was powered down too long) you may need to replace the battery.

If this is not the case then the controller PCB may need to be replaced, or the caps need to be checked.
I've tried flipping the switch both ways in case rubbish was stored in the memory. Still the same.

Apologies for the adverts

Ta, I'll look at that tomorrow.

I would also check all the wired/plugs connections, the connectors may need a bit of a wiggle to connect.
I've taken the top off and done that to all that I can see but there are more deeper inside that I can't reach easily.

I emailed several repairers around the UK but none are up and running again yet. One did, however, suggest "try checking as many voltages as you can especially in region of processor and frequency synth." In preparation for that I've started printing out the Service Manual. The PDF is very dark and the large A3 pages are scanned onto three A4 pages so I'm currently working my way through them and copy-&-pasting the scans onto an A3 page in MS Word. Six down and eighteen more to go!
 

Terryl

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I just download the PDF file, and view it on my PC.

The one I looked at was very clear....http://pdf.textfiles.com/manuals/SCANNERS-S-Z/Yaesu-FT-726R%20Operating%20Manual.pdf
 

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Well the thing is, if that battery is dead it maybe a voltage problem in the memory circuit, removal or replacement would be a tell.

It does have a blocking diode after the battery to prevent this from being a problem, but what I don't see in that circuit is a way to recharge the battery.

Here is a blow up of the memory circuit, Q02 and Q03 are the memory IC's, they get their VCC from the two diodes D12 or D13 depending on the power conditions, there maybe a problem in that circuit.

FT 726R control PCB.jpg

This control PCB handles the display.
 

Terryl

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Also check page 9 section 22, it says that is the repeater shift is outside the normal band limits it will display a E, change RPT SELECT to something else and see what happens.
 

Terryl

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The big bummer is if this battery or the controller PCB has a problem it's very hard to get to, it is mounted on the front panel, and would require removal or disassembly of the front panel.
 

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The big bummer is if this battery or the controller PCB has a problem it's very hard to get to, it is mounted on the front panel, and would require removal or disassembly of the front panel.

If it is like the Yamaha DX synths of the 80's, it could be a button cell, which is hard soldered and does not get any charge. They can last upwards of 25 years though.

Fit a battery holder once you have opened it all up.
 

PaulR

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Thanks for all your research Terryl. I didn't mean that the PDF was unreadable, just that the copy of the operating manual that came with the rig was better photocopied or scanned. For one thing, the fold-out pages are printed on one large sheet, not just over three A4 pages.

I've spent most of today (in between other things) working on the service manual to restore all the fold-out pages there. it took a while but now it's done I just have to punch holes in the pages and find a folder for them. I much prefer reading off paper compared to off a screen when I'm trying to get to the bottom of a problem.

I'll have to leave all the investigation until tomorrow now. Providing the good weather doesn't tempt me away that is...
 

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One of our local ham club members is a whizzer at repairing old rigs, though he prefers the vacuum variety.

I've left him a message but it's unlikely he will reply before the weekly club meet, which is next Tuesday.
 

Terryl

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I'd give the RPT SELECT switch a few twists to see what happens, it may be dirty, I have that problem with my FT 847, but it's a major job to get to it to clean it.

In the info for this unit it mentions that if this switch is in the wrong setting it will display an E error.
 

PaulR

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I wasn't able to do much more than have a quick scan of the manuals today (I was collared to do some household painting) but if I read the manual correctly the E message for an out of band repeater shift is displayed only when you try to transmit. Is that right?
 

Terryl

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I wasn't able to do much more than have a quick scan of the manuals today (I was collared to do some household painting) but if I read the manual correctly the E message for an out of band repeater shift is displayed only when you try to transmit. Is that right?
It says transceiver, so that may be both TX and RX, don't know, wish I had one to test for you.
 
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