Uniden Tempo 2020

[kopcicle]

It's parentage sometimes confused with Yaesu (the Tempo One was Yaesu) and the Uniden applied to other than the US radio which was Henry, The 2020 is an interesting Hybrid in two ways. First it uses the 12BY7A driver and the 6146 pair as do many other Hybrids. Second is the curious Hybrid synthesizer that not only uses a dial for the last digits but spans 100KHz in 5 steps. The Yahoo group dedicated to Tempo 2020 is a great resource.

Now onto the "fun"

My 2020 came to me with a broken sprocket set. This makes the radio useless. With many thanks to Wald, N4PL and Gregory, NR6C I proceeded to restore this radio.

This is typical of ALL of these 30 plus year old radios . There have been adaptations of other sprockets and temporary fixes that used small clamps, tie wraps, tie wraps and glue or circlips. Forget about it , all of it . f you are going to get into the radio at all, do it right.

A thing of beauty. These are 3D printed and machined centers. They are made from a much more stable plastic and should outlast the radio or operator. My only suggestion to to Greg was to include a couple extra setscrews as they are easily lost. It is so very rare these days that you can close your eyes, sign the check. and be happy. That is exactly what happened here. The ID of the sprockets was so close that minor stoning of the shafts was in order to remove burrs from the original set screws.

As you can see if just one of these sprockets is off the radio is essentially junk. I'll admit to having to do the install no less than three times as I was "one off" the first two times. I got pretty good at getting into the front of the radio which I'll share next .

Many thanks to W7CPA, N4PL and NR6C for the images and text
W7CPA here
http://www.arizona-am.net/PHOENIX/W7CPA/Tempo 2020 Restoration Notes.pdf
NR6C here
http://nr6c.com/TEMPO SPROCKETS.htm
N4PL here
https://groups.yahoo.com/neo/groups/TEMPO_2020/info

 

[kopcicle]

Front panel removal
is required to change lamp inside drum, replace toggle switches and fix/replace
sprockets.
1.
Remove top and bottom covers.
2.
Remove front bezel by unscrewing all stainless counter sunk Phillips screws top, sides and bottom. Carefully pull forward. This was a very tight fit on my 2020.
3.
Remove the following knobs:
PRESELECT, PLATE, LOAD and BAND MHz.
4.
Remove the top Phillips to the right of center that secures the front to the chassis
5.
Remove the bottom Phillips to the left of center that secures the front to the chassis.
6.
Carefully rotate the front panel forward to clear the PRESELECT, PLATE, LOAD and BAND
MHz shafts. It has hinges on the bottom that allow a 90 degree tilt forward over the edge of a
desk – a very nice design.
7.
Be careful rotating the front panel down since the mode switch has exposed diodes on the back.
I had one break off the lug.
http://www.arizona-am.net/PHOENIX/W7CPA/Tempo 2020 Restoration Notes.pdf

Above from W7CPA

I recommend that the radio with out its covers be placed on the bench with the front 2" hanging off the bench to make the "side and tilt easier. Also these are old radios and the wiring on the bottom of the chassis needs to be protected. Just a inch or so of some support under the outside chassis rails will elevate the wire looms.

While you are inside the front panel replace the bulbs and service anything else you may need to as it really isn't that difficult but it does take time.

Next , audio...

 

[kopcicle]

Using a crystal element (as delivered in a Turner 254 desk mic) the hum disappeared . The audio was a bit low so I dug into the TA7063p data sheet and found the spec was a 22k ohm feedback resistor . The bit in the radio was a 6.8K ohm . I installed a 15k ohm at R551 and replaced the 4.7uf output cap at C532 with a 10uf . There is a capacitive resistance network on the input to the TA7063p but didn't play with it . ( C529 , R547 a 10k through followed by a 100pf to ground and the 100p at C527 . Q506 then has its part to play . )

I finally settled on an old Shure Brothers 520B controlled reluctance cartridge that just likes my voice.
Do be aware that Ground is Ground but Shield is Shield . Confuse the two connections to the mic input and curious things happen.

 

[kopcicle]

I had a conversation with Nomad Radio today and other than the usual BS I got talked into writing this up . It's a great radio that deserves a better fate than the junk heap just for the lack of sprockets.

It's all Nomad's fault , that's my story and I'm sticking to it !

NOTE:
If you have a Kenwood Hybrid with the same issues , NR6C also produces those parts as well .

 

[kopcicle]

appears to be a 120cy issue. main, bias, screen, AVR ? It's an epidemic, all three radios now have the issue :-/
The TX audio was choked off miserably on two to the point I changed the feedback resistor on two of them and disabled the ALC signal on another. This is what I get with any MIC gain at all with any type of mic. :-(
A hand full of caps and I'll get back to this ...

 

[Rwb]

View attachment 26004
appears to be a 120cy issue. main, bias, screen, AVR ? It's an epidemic, all three radios now have the issue :-/
The TX audio was choked off miserably on two to the point I changed the feedback resistor on two of them and disabled the ALC signal on another. This is what I get with any MIC gain at all with any type of mic. :-(
A hand full of caps and I'll get back to this ...

it amazes me how some here are great with radios. You are 1 of them,few more i watch are too
Kind of like my old school gunsmith,he worked the crappy sight adjustmeers over on my ruger mini 14 ranch rifle you could never get it set dead true ,either off to the right or left ,never centered.he fixed both elevation and windage. When done it looks as it was built

 

[Riverman]

How about a pic of the front of the radio for those of us who aren't familiar with the Tempo 2020?

Thanks!

 

[Handy Andy]

120AC 60 Hz - Full wave - brings it to 120Hz - could you have a ballast or line ballast system going on in there? Not in the radio - a ringing effect caused by a line conditioner...

120Hz is usually caused by rectification within an isolation or step up/down transformer line load power conditioner with bad or noisy rectifiers.

 

[Handy Andy]

How about a pic of the front of the radio for those of us who aren't familiar with the Tempo 2020?

Thanks!

PDF attached too...

 

[kopcicle]

yup, from Randy, W7CPA

 

[Shadetree Mechanic]

View attachment 26018

PDF attached too...

Ok now I want one.

 

[nomadradio]

Excellent receiver, stable VFO, smooth transmit audio.

Just one fatal flaw, besides the age.

The "Preselect" knob is connected to three tuning capacitors inside, ganged together with plastic cog wheels. One of them peaks the receiver input, one peaks the transmitter's driver and the other one peaks the mixer stages.

The plastic shrinks, and cracks around the setscrew. This knocks the three tuning capacitors out of sync. Bad news, since they must all three be peaked together when the knob is turned.

Oops.

The solution is metal cog wheels. Not cheap, but this takes care of that problem, once you get them back each in sync one with the other two.

The cause of the 120-Hz ripple problem should reasonably appear on the output of one or more of the voltage regulators.

Could be a bum regulator, could be a failed filter cap on that regulator's input side?

The ripple at the root of the symptom should be visible on a 'scope, though.

73

 

[kopcicle]

Ok now I want one.

just setup rss for craigslist and a ebay notification. join the yahoo group. I can ask a Bridgeville, Pennsylvania op if his is still for sale...

 

[kopcicle]

The plastic shrinks, and cracks around the setscrew. This knocks the three tuning capacitors out of sync. Bad news, since they must all three be peaked together when the knob is turned.

That's the circlip fix , it didn't work.
http://nr6c.com/TEMPO SPROCKETS.htm well worth it . Without it it's a paperweight. The one thing that's kinda convenient about the sprocket failure is even if the seller knows it's fubar thay don't want to mess with it and the radios come cheap.

 

[Shadetree Mechanic]

just setup rss for craigslist and a ebay notification. join the yahoo group. I can ask a Bridgeville, Pennsylvania op if his is still for sale...

Thanks, I won't be able to make the purchase until after the holidays. For now I'm am just looking.