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Author Topic: Tempo One ( Yaesu FT-200 ) restoration and thoughts  (Read 818 times)

HAMHOCK75

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Tempo One ( Yaesu FT-200 ) restoration and thoughts
« on: September 30, 2022, 02:00:00 PM »

I bought a Tempo One two years ago from a ham who said it had not been used for 20 years. It is a mostly tube transceiver with few semiconductors in select places. It was a Yaesu FT-200 imported by Henry as the Tempo One in the early 1970's. It preceded the extremely popular FT-101 series. The front panel layout is very similar to the FT-101 except that internally the 101 was mostly semi-conductors with only three tubes remaining. The same three tubes are in the Tempo One, the 12BY7A driver and a pair of 6JS6A finals. The FT-100 also differed in that it did not have an internal power supply. The AC power supply came in a speaker box. The DC supply was also separate. The FT-101 had both AC and DC power supplies internally.

It was a lower end rig when introduced to compete against HW101's, etc. Tempo's have not held their value very well especially compared to FT-101 which often sells for $300+, the Tempo One can typically be had for less than $100 with AC power supply with speaker. Heathkit DX-60's typically sell for more.

Unlike my FT-101 restoration which took a lot of work because it had been used and abused by CB'ers, this Tempo has required not that much work. I have written about a few repairs and tests of the Tempo One on these previous threads.

Servicing the ANL switch

https://www.eham.net/community/smf/index.php/topic,132535.msg1214638.html#msg1214638

7360 tube solid state replacement

https://www.eham.net/community/smf/index.php/topic,132825.msg1218533.html#msg1218533

CW mode

https://www.eham.net/community/smf/index.php/topic,133419.msg1226974.html#msg1226974

Some time was spent recently removing corrosion was found in the grid control capacitor.



A GPSDO was used to calibrate the 100 kHz calibration crystal oscillator to within 0.1 Hz. The lower blue trace is the 100 kHz oscillator signal at the collector of TR301.



Then calibrated the front panel with the crystal calibrator signal. The manual does not explain how to do that so I spent a few moments with the spectrum analyzer to show how it is done and the result.



In the photo above, the frequency is set to 21 MHz, then the “CAL” knob is used to mechanically hold the dial from moving while the tuning knob is free to tune the VFO. The manual never mentions what to the tune the VFO for but it is “zero beat”. Tuning from high to low audio frequency, after the low audio disappears, by listening very carefully, a low level audio signal increasing in frequency can be heard. The null between these two events is zero beat.

What the front panel readout of frequency represents when this is done is the carrier frequency in SSB mode. The frequency below is the 21 MHz carrier leaking out and picked up with a probe when the above calibration is done.






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WB8VLC

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #1 on: September 30, 2022, 02:58:58 PM »

It's an ok starter radio and this one was my first novice rig in 75.

I worked that radio to death on CW with over 200 dx entities worked as a novice and a single 15 meter 3el yagi on my parents roof outside of Detroit during 1975 and 1976 on CW only.

The radio only has a single wide SSB filter and nothing meant for cw but what did I know back in 1975, in those days you took what you had and made it work and that radio sure got a workout.

It wasn't until my wife bought me a Kenwood TS690S with a real CW filter in 1992 that I realized what I was or wasn't missing, as  result of using that radio on CW with the wide ssb filter I learned to pick out and copy weak CW in between several other loud adjacent cw stations.
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #2 on: October 01, 2022, 07:13:34 AM »

Quote from: WB8VLC
I worked that radio to death on CW with over 200 dx entities

When responding to a CQ, do you recall the procedure for tuning to that station? Did it involve the use of the Clarifier?

In the meantime, a solution to a "Tune" problem.

Tempo One Tune Mode

The “Tune” path is shown below. The 1.5 kHz side tone is applied to the microphone amplifier to mix against one of the two carrier frequency crystals, ( 8,998.5 kHz for 40 and 20 M, 9001.5 kHz for 80, 15, 10 M ) producing a 9 MHz signal to pass through the center of the SSB crystal filter passband.



Below the spectrum analyzer shows the leakage of the carrier and USB side tone on 15 M. The side tone is injected at a low level to show its position relative to the carrier.



A problem was found with the tune mode caused by drift in the RC oscillator generating the 1.5 kHz side tone. The side tone drifted to above 2.2 kHz which was then cut off by the crystal filter reducing available drive.

Below the frequency setting components were removed from the RC oscillator and examined on the left. The replacement parts are on the right. The Tempo One does not have a fan. The measured temperature increase on the RC oscillator board was about 40 degrees F. above ambient room temperature. Such a large temperature rise contributed to the frequency drift.



R512 is a carbon composition, 22k resistor. It had changed value to 26k which is out of specification for a 10% part but it’s temperature drift when heated with a hair dryer was reasonable. R511 at 33k was within tolerance but had greater drift than R512. The culprits for drift were C505 and C507 both .01 uF. These ceramic disk capacitors measured .0124 uF with a Fluke 87. They decreased in value by about 25% with heat from the hair dryer. C506 did not change much. None of these capacitors had any markings other than their value. All the carbon composition resistors showed a negative temperature coefficient.

VR503 was replaced with a cermet trimmer, C505, 506, and 507 were replaced with Mylar capacitors with a slightly positive temperature coefficient. R511 and R512 were replaced with metal film resistors. The drift as the temperature rose from room temperature to 113 degrees F was improved considerably but was still about +300 Hz.

Using a hot soldering iron to touch the remaining components, it was found that C504 ( serving as a coupling capacitor ) and C510 ( serving as a bypass capacitor ) where the main contributors. These were once again .01 uF ceramic disk capacitors like C505 and C507. After these were replaced the RC oscillator drifted from 1524 Hz cold to 1506 Hz after 17 minutes where it stayed for 80 minutes which was the duration of the test.
« Last Edit: October 01, 2022, 07:36:05 AM by HAMHOCK75 »
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WA4MDP

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #3 on: October 01, 2022, 03:50:43 PM »

I just found one today! Its listed on QTH.com if anyone's interested in restoration. As the author said the price is right :)
'73 WA4MDP
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N8CBX

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #4 on: October 03, 2022, 06:29:02 AM »

I have the silver, front panel Tempo-One and I will be repairing it this winter.
I'll be following along with your rebuild thread.
Jan N8CBX
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WB8VLC

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #5 on: October 03, 2022, 09:24:40 AM »

RE: using the clarifier question: Yes I would set the VFO as close to the other station and then leave it alone and then I used the clarifier/RIT to keep him in tune on RX.

I built up a 750 Hz wide  CW audio filter that I connected to the External VFO switch so that during CW I could switch the filter in and then I had some degree of better filtering for CW and even though it was at the audio end it worked  much better than the single SSB filter on CW.

I also used AM a lot on 15 meters and the radio was very good for that mode.
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #6 on: October 03, 2022, 11:12:42 PM »

The CW mode of the Tempo is much easier to use than to understand.

The Tempo One CW mode requires the use of the Clarifier. This is why the Clarifier control has CW1 and CW2 written on the front panel but unfortunately they are not mentioned at all in the operating manual. There is no explanation for how those positions are used. The Clarifier markings indicate about 1 kHz steps.

Below is a photo of the Tempo One front panel band switch and Clarifier. Bands with white numbers use a 9001.5 kHz carrier crystal. Ones in red use the 8998.5 kHz carrier crystal.



Below is a diagram of how the the Tempo One works in CW mode on 20 M.



On receive, the incoming 14 MHz signal mixes directly with the VFO at 5 MHz to create a 9 MHz IF signal. The IF signal mixes with the 8998.5 kHz crystal oscillator to produce an audio output at 1.5 kHz.

The transmit frequency will not be 14 MHz however. The leakage of the 8998.5 kHz carrier oscillator past the 9 MHz SSB filter is used to mix against the first LO to create the transmit signal. If the VFO remains at 5 MHz during transmit, then 5000 + 8998.5 kHz = 13998.5 kHz. The transmit signal will be 1.5 kHz below the received signal.

To remove this offset, turn on the Clarifier; set to the CW2 position on 40 and 20M. Tune using only the VFO until the desired CW signal tone sounds like 1.5 kHz. This can be compared to the pitch of the Tempo One side tone which is set to 1.5 kHz. The Tempo One will now transmit at the same frequency as the received CW signal. Do not use the VFO to tune further. The above procedure corrects the VFO so that the transmit frequency matches the incoming signal frequency. Use the Clarifier to adjust for a comfortable listening tone after the VFO position has been set.

The explanation of why this works is as follows. The use of the Clarifier set to position CW2 lowers the VFO frequency by 1.5 kHz. To compensate the VFO must be tuned to 5001.5 kHz to eliminate the offset created by the Clarifier so the LO frequency is once again 5 MHz during receive.

When the Tempo One goes to transmit mode, the Clarifier offset is eliminated so the rig transmits on 5001.5 kHz + 8998.5 kHz = 14 MHz, the same frequency as the incoming received signal. The use of the CW2 position is simply to cause the VFO to be tuned to 5001.5 kHz. Once that is done, the VFO is not tuned again since it is at the correct frequency needed for transmit. The Clarifier can now be adjusted for a comfortable listening tone since it only works during receive.

There is a potential complication on the bands that use the 9001.5 kHz carrier crystal. The rejection of the carrier by the SSB filter is greater for the 9001.5 kHz carrier than for the 8998.5 kHz carrier. To get around that, the Tempo One uses a varactor to tune the 9001.5 kHz carrier oscillator 200 Hz lower in frequency to 9001.3 kHz. This provides more carrier leakage for the 9001.5 kHz crystal which is desirable in this case.

Tuning a CW signal on the 80, 15, and 10 M bands is similar to 40 and 20 M except the Clarifier is set to CW1 which creates an offset of about +1.3 kHz. Tune for a 1.5 kHz tone with the VFO as before on 40 and 20 M. This will place the VFO at 5.4987 kHz to cancel the Clarifier’s +1.3 kHz contribution as shown in the figure below. Once the VFO position is set, the Clarifier may be adjusted for a comfortable listening tone as before.



Although the CW1 position may appear on the front panel to be a 1.5 kHz offset it is not due to the actual characteristic tuning curve of the Clarifier shown below. The Clarifier turned counter clockwise from the “zero” position compresses so that CW1 which looks like 1.5 kHz is closer to 1.3 kHz.

I should point out that the Clarifier has two sets of markings, one in white in one in red depending upon the output band. The graph below is data taken at the VFO using the white markings as a reference.

The Clarifier on this Tempo One had an actual CW1 offset of +1.388 kHz and a CW2 offset of -1.975 kHz.



The Tempo One Clarifier has no gain calibration adjustment only an adjustment to set the “0” to the same frequency as when the Clarifier is off. To add a calibration adjustment a 500 k cermet trimpot was soldered across the end terminals of VR7 which is the Clarifier potentiometer. The cermet trimmer was then adjusted so that CW2 gave a +1.5 kHz offset. The measured CW1 offset was 1.312 kHz as shown below.



The photo below shows the actual shift of the 9001.5 kHz carrier is about 182 Hz.



Below is a test of how close I was able to zero beat the incoming signal using the method described above. The signal in the center is from an Icom 705. This was on 15M. The Clarifier was set to CW1, then the VFO tuned so the received tone from the 705 matched the Tempo’s 1500 Hz side tone. The lower signal to the left of center about 35 Hz away from the 705 signal is the Tempo One transmit carrier in CW mode.



To tune a CW signal on 80, 15, and 10 M, set the Clarifier to CW1, tune the VFO for a 1500 Hz tone matching the Tempo One side tone. This zero beats the incoming received carrier with the Tempo One transmit carrier. Use only the Clarifier to obtain a comfortable listening tone after zero beating.

The same procedure on 80 and 40 M but use CW2.
« Last Edit: October 03, 2022, 11:18:40 PM by HAMHOCK75 »
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #7 on: October 09, 2022, 05:48:01 AM »

Capacitor tests

More of the .01 ufd, 50 volt ceramic capacitors which fared so poorly in the RC oscillator circuit were removed for testing. In the photo below, the group of six ceramic capacitors under the ruler came from the 7360 solid state replacement board. The group of five to the right of those are from the amplifier board that follows the VFO. Off the right end of the ruler, the blue dot is a X7R .01 ufd ceramic capacitor. To the right of the blue dot is a .01 ufd, 500 volt capacitor taken from the Tempo One.



Each capacitor’s initial value was measured using the Fluke 87 multimeter. The hair dryer located about three inches to the left of the capacitor being tested was turned on for 10 seconds, the value of the capacitor was measured. C202 is from the heterodyne oscillator board. The results are below.



Without knowing what kind of specifications these .01 ufd, 50 volt capacitors have, they seem to have uniformly poor temperature performance. No other ceramic capacitors in the Tempo One have been found with this poor performance.
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KX4OM

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #8 on: October 09, 2022, 08:15:55 PM »

Good thread, guys. I have the power supply for these rigs, and I'm thinking I may need to seriously start thinking about finding one of them to refurbish.

Ted, KX4OM
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #9 on: October 12, 2022, 02:11:30 PM »

Quote from: KX4OM
I may need to seriously start thinking about finding one of them to refurbish

If you have ever refurbished a Heathkit, the Tempo One will be familiar. The carbon composition resistors in these units tend to change value. I do not recall ever seeing carbon composition resistors used in a Japanese rig before. It's hard to remember if carbon composition was cheaper than carbon film back in the late 1960's, early 1970's.

It is unlikely that Yaesu would knowingly use such poor, high drift capacitors in sensitive applications as the RC oscillator. They might have received a bad batch or they were ok 50 years ago but have aged poorly.

I am replacing all of the .01  ufd, 50 volt parts. C50 was the most difficult part to replace because of the location. C46 is shown in the material list but so far cannot be found on the schematic or the unit itself.

Unfortunately, the material list shows C401, 405, 407, 411, 416, 418 in the VFO assembly. The schematic shows an additional C422 in the VFO assembly.
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #10 on: October 16, 2022, 02:53:51 AM »

Drift Of The Power Supplies For The VFO

The VFO runs off the regulated +9 VDC supply. This supply also via voltage divider R39 ( 47k ) and R40 ( 47k ) provides 4.5 volts for the Clarifier varactor when Clarifier is not used. If the +9 volt supply drifts, this could contribute to VFO frequency drift. The +9 volts was monitored with a 4.5 digit HP multimeter. The results are below.



The carbon composition resistors that are mostly responsible for the accuracy and drift of the 9 volts and Clarifier voltage when the Clarifier is not engaged were then replaced with metal film resistors. These resistors were R504, 505 in the regulator and R39, 40 in the Clarifier circuit. Since the Clarifier voltage is the 9 volts divided in half and represents both the 9 volt drift and the Clarifier drift, the Clarifier drift was measured with the results below.



The approximately 40 mV drift with carbon composition resistors is reduced to about 6 mV ( assuming the 9 volt drift is about twice that measured at the Clarifier ) for a 40/6 = 6.7 fold improvement.
« Last Edit: October 16, 2022, 02:56:23 AM by HAMHOCK75 »
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N2EY

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #11 on: October 17, 2022, 09:19:00 AM »

Good thread, guys. I have the power supply for these rigs, and I'm thinking I may need to seriously start thinking about finding one of them to refurbish.

Ted,

I have a black-face Tempo One that needs TLC. It's all there but has seen better days. Receives but transmit needs work. Also have PSU but willing to separate them.

I'm in 19087 so shipping shouldn't be too bad.

73 de Jim, N2EY
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N2EY

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #12 on: October 18, 2022, 05:08:17 AM »

Drift Of The Power Supplies For The VFO

The VFO runs off the regulated +9 VDC supply. This supply also via voltage divider R39 ( 47k ) and R40 ( 47k ) provides 4.5 volts for the Clarifier varactor when Clarifier is not used. If the +9 volt supply drifts, this could contribute to VFO frequency drift. The +9 volts was monitored with a 4.5 digit HP multimeter. The results are below.



The carbon composition resistors that are mostly responsible for the accuracy and drift of the 9 volts and Clarifier voltage when the Clarifier is not engaged were then replaced with metal film resistors. These resistors were R504, 505 in the regulator and R39, 40 in the Clarifier circuit. Since the Clarifier voltage is the 9 volts divided in half and represents both the 9 volt drift and the Clarifier drift, the Clarifier drift was measured with the results below.



The approximately 40 mV drift with carbon composition resistors is reduced to about 6 mV ( assuming the 9 volt drift is about twice that measured at the Clarifier ) for a 40/6 = 6.7 fold improvement.

Great stuff! I wonder how much this voltage drift translates to actual frequency change?

Also - what are your thoughts on replacing the discrete-parts 9 volt requlator with a 3 terminal regulator?

73 de Jim, N2EY
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #13 on: October 18, 2022, 10:06:22 PM »

N2EY,

I have not taken data on the drift of the VFO. The material list and schematic suggests that the VFO may contain seven of the bad .01 ufd, 50 VDC ceramic capacitors ( C401, 405, 407, 411, 416, 418, and 422 ). If that proves to be true, they will all be replaced prior to any drift test.

Quote from: N2EY
Also - what are your thoughts on replacing the discrete-parts 9 volt requlator with a 3 terminal regulator?

As a restorer I would not usually do that since restoration involves maintaining the rig as close to factory as possible. For those not interested in restoration as much as repair or even improving upon the unit, then it may be a good idea from a reliability point of view but not necessarily for improved performance.

For example, a 7809 regulator could conceivably replace nearly all the discrete parts in the +9 V regulator but the drift specification of the 7809 is -1 mV/degree C ( see link below for specifications )

https://pdf1.alldatasheet.com/datasheet-pdf/view/888521/SEMTECH_ELEC/7809.html

The measured temperature change at the +9V regulator/RC oscillator board is about 23 degree C, so the typical drift with the 7809 might be around -23 mV vs 40 mV for the unmodified regulator with carbon composition resistors. As described earlier the 40 mV drift  can be improved considerably just by using metal film resistors.

The 7809 should be more reliable since it eliminates a large number of parts and soldered connections including the adjustment potentiometer, VR501.

Before I changed the four carbon composition resistors, I was sent this link which contains a modification to use a common three terminal regulator, the 7805.

http://vk2yld.info/ft200.htm

I have no idea how many hams might have followed this change, but I am not sure the problem was ever really solved since the drift after the solution is still 130 mV which is more than three times worse than the unmodified but properly functioning regulator.
« Last Edit: October 18, 2022, 10:08:27 PM by HAMHOCK75 »
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HAMHOCK75

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Re: Tempo One ( Yaesu FT-200 ) restoration and thoughts
« Reply #14 on: October 19, 2022, 11:18:45 PM »

Grid Tuning Capacitor

The schematic does not identify how sections of the “grid” tuning capacitor are connected.



The left most small section of the six section air variable capacitor is connected in series with C22 ( 50 pF ). It and C22 are connected to the plate of the pre mixer only on 10M. The next large section is not used.

The center left small section is connected to the trans mixer plate. The adjacent large section to it’s right is in series with C30 ( 350 pF ). The large section with C30 are only switched in parallel with the small section on 80M.

The small section on the far right is connected to the driver plate. The large section to it’s left is in series with C37 ( 300 pF ). The large section with C37 are only switched in parallel with the rightmost small section on 80M.
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