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Author Topic: Fixing FTdx560: First Tube Radio  (Read 408 times)

KN6LMJ

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Fixing FTdx560: First Tube Radio
« on: April 20, 2022, 09:21:46 PM »

Hi all, I'm working on an FTdx560 I recently bought on Ebay. I have some solid state electronics experience but not a ton. I also have a friend helping me who has rebuilt guitar tube amps, so between us we have some knowledge.

I have an Oscope and a variac that I figure will come in handy along with an incandescent light bulb socket.

The transceiver is missing the final tubes but I was able to purchase from a friend of a friend for a great price.
It's also missing all the sheet metal tube shields, the bottom panel of the chassis. I think I found the right ones on Ebay.

The part that concerns me right now, is a missing LSB crystal (part 201) that is 3181.5 KHz. I have not seen any on Ebay and I don't know what that particular package is called.

I'm hoping someone here knows how to search for them, has one, or knows where to buy one. Or perhaps there's a hack with a modern crystal ??

TIA, 73, LMJ


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AJ9C

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Re: Fixing FTdx560: First Tube Radio
« Reply #1 on: April 21, 2022, 05:30:30 AM »

Check with AF4K (Google it) They sell all manner of crystals and holders.
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VK6HP

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Re: Fixing FTdx560: First Tube Radio
« Reply #2 on: April 21, 2022, 06:40:20 AM »

I restored an FTDX560 a couple of years ago.  As I recall the BFO crystals are HC-6/U types which are relatively widely available, although a newer holder size should be OK in the relatively non-critical and low-ish drive circuit.  There are several suppliers left who make custom crystals if you can't find a used device. Send them a copy of the oscillator schematic when you order.

One caution re used and original crystals: the crystals in the Yaesu were spectacularly awful in terms of frequency aging and activity level.  Fortunately, most could be tweaked back into tolerance in my transceiver but the difference between the FTDX-560 and a Collins 32S-3 from the same era was stark.  Before you get too far into the repair you might also want to have a look at the crystal filter.  By carefully setting up the BFO frequencies I was able to get pretty good USB and LSB audio on transmit and receive but I gave up on the idea of trying to obtain a CW filter - there weren't enough variables left to juggle!

Be gentle on the sweep tubes when you fit them, and make sure you read the manual regarding tuning the PA.  You need to be quick and accurate.  My radio managed a genuine 300W CW/PEP output on new tubes but, if you value your ham neighbours, don't run it at anything like that SSB level.  About 120 W PEP out gives just OK IMD but at 300 W you're in the IM3 ~ -20 dBc territory which is, in fact, about consistent with the original spec of -25 dB with respect to PEP.

I also replaced the hardest working electrolytic capacitors (including the can types) and quite a number of tubes (including the 7360 balanced modulator).  With careful alignment the radio turned out well and was something of a nostalgia blast, my late 70s first "real" radio having been an FTDX401B.

There were many modifications throughout the series to try and correct Yaesu's weird mic amplifier design but often the easiest way is just to use a high output (or amplified) mic and roar at it.  Better mods move the mic gain pot to the right place and fix the negative feedback fraction.

73, Peter.
« Last Edit: April 21, 2022, 06:44:51 AM by VK6HP »
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KN6LMJ

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Re: Fixing FTdx560: First Tube Radio
« Reply #3 on: April 21, 2022, 09:43:01 AM »

VK6PH, thanks a ton that helps. I'm not sure if I have the skill to handle some of the tasks you outlined. I'll give it a try  after a lot of research.

I see now that the crystal package is called HC-6/U on the spec sheet. I saw on a website that the HC48C is very similar with minor difference in soldering. I don't really understand how the LSB/USB part of the filter ciruict work so I guess that'll be my new learning focus.

Cheers
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KN6LMJ

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Re: Fixing FTdx560: First Tube Radio
« Reply #4 on: April 21, 2022, 09:45:35 AM »

Check with AF4K (Google it) They sell all manner of crystals and holders.

Yes I found them. It took me several minutes to figure out where the actual list of crystals were, hiding at the bottom of the page in buttons :|

I didn't see my crystal but I did email the owner. I hope something comes up.
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N8YX

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Re: Fixing FTdx560: First Tube Radio
« Reply #5 on: April 21, 2022, 09:56:15 AM »

Check the BFO crystals from an FT-101 series. IIRC they used the same ones. And an entire board can be had relatively cheap on the auction site.
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N5KBP

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Re: Fixing FTdx560: First Tube Radio
« Reply #6 on: April 21, 2022, 02:25:38 PM »

As N8YX mentioned the old FT101 series not the FT101Z used the same crystals. You will need to look for an old PB-1184 board.
Marty
N5KBP
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KN6LMJ

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Re: Fixing FTdx560: First Tube Radio
« Reply #7 on: April 21, 2022, 09:32:36 PM »

Big thanks to Marty and N8YX.

I just bought this PB-1184 board for a reasonable price. Not sure if I should have gotten the more expensive units.

https://www.ebay.com/itm/234391742926?hash=item3692d629ce:g:C6gAAOSwdalh71X3
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KN6LMJ

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Re: Fixing FTdx560: First Tube Radio
« Reply #8 on: April 30, 2022, 09:19:08 AM »

 @VH6HP Should I use a variac ?

I restored an FTDX560 a couple of years ago.  As I recall the BFO crystals are HC-6/U types which are relatively widely available, although a newer holder size should be OK in the relatively non-critical and low-ish drive circuit.  There are several suppliers left who make custom crystals if you can't find a used device. Send them a copy of the oscillator schematic when you order.

One caution re used and original crystals: the crystals in the Yaesu were spectacularly awful in terms of frequency aging and activity level.  Fortunately, most could be tweaked back into tolerance in my transceiver but the difference between the FTDX-560 and a Collins 32S-3 from the same era was stark.  Before you get too far into the repair you might also want to have a look at the crystal filter.  By carefully setting up the BFO frequencies I was able to get pretty good USB and LSB audio on transmit and receive but I gave up on the idea of trying to obtain a CW filter - there weren't enough variables left to juggle!

Be gentle on the sweep tubes when you fit them, and make sure you read the manual regarding tuning the PA.  You need to be quick and accurate.  My radio managed a genuine 300W CW/PEP output on new tubes but, if you value your ham neighbours, don't run it at anything like that SSB level.  About 120 W PEP out gives just OK IMD but at 300 W you're in the IM3 ~ -20 dBc territory which is, in fact, about consistent with the original spec of -25 dB with respect to PEP.

I also replaced the hardest working electrolytic capacitors (including the can types) and quite a number of tubes (including the 7360 balanced modulator).  With careful alignment the radio turned out well and was something of a nostalgia blast, my late 70s first "real" radio having been an FTDX401B.

There were many modifications throughout the series to try and correct Yaesu's weird mic amplifier design but often the easiest way is just to use a high output (or amplified) mic and roar at it.  Better mods move the mic gain pot to the right place and fix the negative feedback fraction.

73, Peter.

Would it be helpful to run at lower power with a variac while trying out the radio with finals in place ? I've never used a tube radio at all. I'll study the manual too but it's nice to have an error margin.
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