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Tempo 2020 Restoration Notes

March 2, 2014 – Updated with X-LOCK, VFO Stabilizer Successfully Installed

Added Long Term Heat Testing and X-LOCK Changes to Simplify – Uses Existing RIT VFO Varactor

Network Now vs. the X-LOCK supplied design.

Randy Best – W7CPA

http://www.arizona-am.net/PHOENIX/W7CPA/index.html

SN = 6060025

I’ve written up my restoration notes in hopes that they might be useful to those that take on a 2020

restoration. I collaborated with N4PL on many of these tasty challenges. There are many useful

messages and files on the Yahoo Tempo 2020 Group to learn from. This Group is the best I have ever

seen WRT good technical information thanks to N4PL, KX4OM and others. The first restoration step is

to join: TEMPO_2020@yahoogroups.com

Front View Speaker, Tempo 2020, Stock Microphone and External VFO Model 8010

The Temp 2020 is one of the finest early transceivers I have ever used.

Summary of content (18 pages)

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Tempo 2020 Restoration Notes March 2, 2014 – Updated with X-LOCK, VFO Stabilizer Successfully Installed Added Long Term Heat Testing and X-LOCK Changes to Simplify – Uses Existing RIT VFO Varactor Network Now vs. the X-LOCK supplied design. Randy Best – W7CPA http://www.arizona-am.net/PHOENIX/W7CPA/index.html SN = 6060025 I’ve written up my restoration notes in hopes that they might be useful to those that take on a 2020 restoration. I collaborated with N4PL on many of these tasty challenges.
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Front View I would then download the user and alignment manuals and all the N4PL files plus the 3 flavors of sprocket repair. The annotated schematics are excellent. Use these in combination with the User Manual module schematics. After all this fun, I strongly suggest not attempting to work on this rig unless you have RF circuit lab tech experience and a pretty robust set of lab equipment with a calibrated VTVM like and HP-410C and a quality frequency counter.
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. Measure driver and PA tube voltages. The Alignment Manual has tables with the proper voltages. Make sure the 6146B screen grid 200 VDC regulation has not been molested or has an open zener. CB Exorcism One of my brand new 6146W experienced an internal short (explosion white splat on the side, blown fuse, open filament etc). Transmit on CB Channels This involves adding a jumper on the Driver board band switch and tweaking the Driver tube output coil.
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Original Cracked Nylon with C-clips Fix Attempt
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New Sprockets and Chains – Whew! Sprocket Alignment The pre-selector alignment is well documented where the chain tensioner needs to go etc. The band switch was challenging so some additional experience notes could be useful. 1. Loosen the tensioner, it slides up and down with a set screw and shaft threading. 2. Install all the new sprockets and don’t tighten set screws. 3.
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c. If you are really anal, you can now rotate the band switch through all positions and inspect the switch contact positions for somewhere close to being centered. Loosen the sprocket set screws and do minor shaft rotations with needle nose for quasi perfection. Front Panel Removal Front panel removal is required to change lamp inside drum, replace toggle switches and fix/replace sprockets. 1. Remove top and bottom covers. 2.
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Low MIC Gain The stock Tempo high output hand mic required the mic gain almost fully clockwise and some bands would never indicate ALC action. I understand the original design was a bit conservative, low noise, high linearity and all that. Since I couldn’t even use my D-104, I had to make changes, stone the crows. The mic amp is on PC-080 - an OP AMP + gain pot + NPN transistor. I download the PC-080 Toshiba Q505 TA7063P datasheet.
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LO Card Band Pass Filter Adjustment My bad past experience tells me never mess with band pass filters to avoid damaging unobtanium coils etc. Since I was having output problems on 15 and 10, I ventured on. The alignment manual references a desired waveform figure but this does not exist. I tried both of the following with good results: 1. Manual described alignment procedures - I also played with my HP sweep generator and spectrum analyzer as well to achieve a nice flat response. Sweep 15.338 MHz to 15.
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under the switch. The parts list does not note matched, but they sure need to be reasonably matched if you want to transmit and receive on the same frequency. Maybe the junction deteriorated over time. I suggest using 1N914/1N4148 diodes matched with a Fluke. My balanced modulator HP diodes work but are really too frail for this duty. PA Neutralization Connect a dummy load and place rig on its side or face down. Set to 15 meters, load up.
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The Model 810 external VFO is relatively easy to add the X-LOCK. You could also do the internal VFO with more mechanical complexity. Only the external VFO is presented here. I experimented with using the standard X-LOCK varactor control network connected to the VFO tuning capacitor. I had to abandon this because of instability after resetting the dial end points – variable L too far away from original design. It turns out the VFO already has a varactor control network used for RIT with a 6VDC supply.
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Conclusions            The oddball hybrid frequency display is amazingly accurate and linear, end to end, on each segment – better than all my vacuum tube Collins gear. Also, one can QSO instantly to CW segment without have to crank the dial forever. The receiver audio is amazingly clean and smooth and fun to listen to. Now my KWM2-A and the Temp0 2020 are my top shelf listening smoothies. The transmit audio gets excellent reports with the stock Tempo mic and ever better with a D104.
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Photo Gallery Back Panel
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Driver Board with DD-103 Interface View Bottom View
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Top View Unique Hybrid Display
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PA Bottom, Note Proper Stud Mounted 200 Volt Zener Diode Operations Board (085) Removed for T/R Delta Diode Fix
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Most Excellent X-LOCK Board VFO Can Removed, 10k Resistor and 2 Connections
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VFO Can Back On and X-LOCK Board Mounted to the Side with Velco
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