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Sunday repair - Broken knob on brand new FT-857D Transceiver.

Updated: Nov 5, 2019

My FT-857 developed a fault the other month, it does not give any power out on transmit on SBB and AM, FM works fine though so the PA is good. The receive section already had some issues since way back so I was getting feed up on all the half working stuff in my lab. Besides the broken Transceiver I also have some moody instruments in the lab. The Anritsu spectrum analyzer was a purchased with a broken screen that I managed to find a replacement for and fix up.

It works fine most of the time but sometimes has intermittent issues with the detector, not a huge problem but sometimes when I do a measurement the line just disappears, argg. :-| Not every time I use it but often enough to be irritating.

peekaboo! now you see me...

now you don't .. :-|

My 2 to 18GHz signal generator is also a fixer-up.

I purchased it with broken front panels, replaced both sections of the front panel and then fixed an PLL unlock error that prevented it from being on the correct frequency and being locked to the nice built-in ovenized oscillator it has as a frequency reference. I troubleshooted it using the excellent HP service manual and managed to trace and find the case of the PLL unlock problem - a faulty trimmer potentiometer. However, after putting it together I found another problem, there is a stuck tuning bit in the PLL that makes it be off in frequency every 8 tuning words when spinning the tuning knob. It will have to wait until I have more time/inclination to fix it so I just work around that problem by not picking a frequency that is affected. Bugs me a little though because it is is super clean and nice otherwise :-)

My nice HP synthesized microwave signal generator

Anyway - back to the non working FT-857D transceiver I reflected over the situation and whether I would try to trouble shoot it myself but decided against it due to time limitations.

At this time I was being feed up of having what I felt was a lab full of broken or half-working stuff!

So I decided to buy a brand new FT-857. I have never purchased a brand new transceiver ever in my life before.

I had purchased this FT-857 in 2010 from an ebay seller in Germany in used condition. But I convinced myself I needed at least one new and good working piece of equipment in my lab, especially now that it is my livelihood. So I shelled up for a new unit from the local distributor here in Sweden and it arrived promptly it is new box and this one came with an included remote head cable set. The remote head means that you can remove the front panel and stow away the radio unit.

This is mainly meant for car installation but I was thinking it would be nice to use in the lab and only have the front panel taking up precious desk space.

So while planing how I would use the separation kit and were to place the front panel on my desk I had the front panel in its wire harness and happened to DROP THE DAMN FRONT PANEL ON THE TABLE AND BROKE ONE OF THE KNOBS!!

So back to having only broken stuff, again :-|

After that unfortunate event I got a bit depressed about the situation and the new Transceiver with it's broken knob just sat in the corner doing nothing. But this Sunday I once again had had enough with all my broken stuff! I was going to fix the broken knob and have a brand new working radio again, and have it working for more than a day this time - period!

As I had the old radio I could just simply move the front panel from that radio over to the new one. What makes it a bit more complicated is that there is a micro-controller in the front panel and there is a nine years manufacturing difference between these radios so it is not unreasonably to believe that they do not have the same firmware versions. Perhaps this would not have been any problem but I decided not to mix them. The new radio would have to have it's new front panel.

My plan was to either replace the optical encoder in the new front panel with a new one if I had a fitting one, or alternatively to move the optical encoder and it's knob from the old front panel to the new front panel.

I labeled up both front panels and started to disassemble them.

I was hoping that I would end up with at least one new working front panel and perhaps even two working front panels. I was aware that there was a slight risk that instead of fixing the bad one with the good one I could would mess up the god front panel and end up with two bad front panels, that would not be unheard of.

In my younger days I visited a TV sales and repair shop that had two identical TVs sitting half assembled in the repair shop and the manager explained with a bitter voice how he had been stuck trouble shooting a customer TV when his his friend came up with the idea of taking a brand new TV from the sales inventory and disassemble so they could compare the voltage readings on different points.

Somehow when he was trouble shooting he happened to mess up the good one as well! Now both were broken and to add insult to injury - they had different problems so he could not compare readings between them anymore. After that they had just been sitting in his repair shop as silent witnesses of good ideas that turned out to be bad in the end. I guess he had become depressed over the whole situation and could not muster enough energy to do anything about it.

Anyway, I knew there was a slight chance this would happen to my two front panels but as I wrote before - I was feed up with all the broken stuff so I just went ahead with the job.

Two front panels being dissembled.

In the end I was surprised how easy it was to fix the broken knob. What is that saying - "Showing up is half the battle". That was certainly true in this case. I happened to have an optical encoder that fit well electrically in the PCB, it's shaft was a bit shorter, some 8 millimeter shorter but I did not overthink it and just went ahead with the repair

The broken one is the green one to the right and the one I ended up using is the blue with metal shaft next to it.

All my encoders I had at home lined up next to the broken original

Everything came together quite quickly and I did not need to cannibalize the old front panel. The twist and click function both works fine and the shorter shaft was not an issue.

New encoder fitted. Putting on a collar for the click function.

The radio is now temporarily on my computer desk until I can decide were it should go more permanently. The old defect radio I will send of to repair if it is not to expensive.

At last - one piece of perfectly fine and working radio gear in the lab :-D

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1 Comment

Really enjoyed reading your detailed account of the various "defects" in your set of equipment, as well as the happy ending for the knob replacement.

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