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 Post subject: Re: Yeasu 101
PostPosted: Jun Tue 12, 2018 10:21 pm 
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Rich,

For cleaning I start with compressed air and a brush to get all reasonably loose stuff out of there. Depending upon the dirt level you might do this outside and for rigs with mouse residue be extremely careful but for most radios a dry cleanup is the best way to start.

I would then pull any plug in boards loose and if the contacts are really dirty physically clean them; otherwise a little WD-40 (emphasis on LITTLE) along with working the board in and out a few times will clean it up and if it has real corrosion issues consider one of the "magic mouse milk" contact cleaners.

A lot of problems in vintage gear is due to bad grounds and slightly loosening and then re-tightening circuit board mounts and grounding points will often make a lot of issues disappear. This is especially common with a lot of tube type Trio/Kenwood gear and Heathkit SB/HW series rigs.

Always make sure that the tube shield on the driver tube is in place and for rigs that came with a heat dissipating shield never use another type. The driver tube is run in class A which means it takes very little feedback for it to take off as an oscillator and it runs very hot so putting a typical reflective shield on it will result in short tube life. Heathkit SB/HW series rigs with the 6CL6 driver will take off in oscillation if the little grounding pin doesn't make good contact with the shield. An oscillating driver tube can quickly take out the finals and the excessive drive in this situation can destroy the control grid even before the anode has a chance to fail from excess heat.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Tue 12, 2018 11:22 pm 
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Thanks alot Rodger. Ill do just that. Ill get this thing cleaned up and check all the connections. Im a new ham so still learning a lot. Thanks!

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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 12:32 am 
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Now i have a new problem. The 5 amp fuse blew. I did the final compartment was very hot after about 30 mins with the heaters on. No talking just listening. Think it might be the 6js6c tubes ?

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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 2:48 am 
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Are the filter caps and the caps on the regulator board still original? If they haven't been replaced at least visually check them and also touch the outside of the capacitors (with power OFF) to see if they are running warm. Any sign of bulging, leaking, or elevated temperature means they should be replaced immediately.

The finals in the FT-101, like many transceivers, have full operating potential on the finals during receive mode and depend upon increased grid bias to keep the tubes cut off. In the receive mode if the bias supply fails then the finals will draw very heavy current which is one reason for transceivers I suggest replacing the bias supply filter caps even if you don't replace any of the others since a bias supply failure will take out the finals and perhaps damage the power supply even though it is sitting in receive mode.

I would turn off the filament supply to the finals to protect them and the power supply then check for proper grid bias, I believe it should run around -65 volts in receive mode.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 12:10 pm 
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Thanks Rodger. I'll check that and since it's almost 50 years old I'm going to replace the caps anyway and give the power supply a good going thru. I think a lot of this relic and would like to keep it going strong. From the looks of it I believe it's been sitting For 40 years no work has been done on it. Not sure why someone would just let it set ..
Thanks

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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 2:26 pm 
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I found c 104 burnt to a crisp and fell apart when I touched it . Not quite sure it's function. Od this be causing problems?


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 2:44 pm 
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L25 and C104 provide a basic low pass filter function as part of the anti-tvi treatment of the rig. C104 shouldn't cause a problem in receive mode but is definitely an issue in transmit mode. I still suspect the bias supply is an issue if the finals are overheating in receive mode although an internal short in the tube would also cause this issue but will generally result in a low bias (or even positive voltage) when measured at the control grid with the tubes in place and the rig in receive mode.

C104 has to be a mica type, 500V minimum. Check L25 for signs of overheating.

C104 could fail from antenna failure while operating at high power, broken coax connection, or a well timed lightning strike.

Check L9 to make sure it isn't open; L9 is the RF safety choke that will short HV to ground and blow the fuse if C23 (DC blocking/RF coupling capacitor) fails leaky or shorted. If L9 is open then also replace C23 with a proper RF rated HV capacitor.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 8:41 pm 
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What pin on the 6js6c tubes would be the bias supply. .. i can tell you i measured the -100 volt off the regulator board and it was upward of -170 vdc.

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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 10:38 pm 
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Pin 5 is the control grid so that will be where you measure the bias. On some varieties pin 9 is internally connected to pin 5 but you can definitely measure it at pin 5 for any 6JS6 variety.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 11:15 pm 
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I checked pin 5 on the 6js6c and had +160v . Heaters not on . But R40 1.5K 5 watt was smoking hot. I was wondering if C13 may be shorted causing R40 to heat up. I had 0 volts across the wire wound resistor 100 ohms which should indicate the tubes are not in oscillation. Sorry for so many questions.

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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 11:16 pm 
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Heres the section


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 11:25 pm 
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Wrong schematic.


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 Post subject: Re: Yeasu 101
PostPosted: Jun Wed 13, 2018 11:27 pm 
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R40 is at the bottom


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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 3:25 am 
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Check to see whether you were on pin 3 instead of pin 5 of the 6JS6 when you measured 160 volts. Positive 160 is correct for the screen grid (pin 3) but definitely not for the control grid (pine 5) which should be around 65 volts negative to ground.

If there is a problem with the bias supply it would also cause the 12BY7 driver and its plate load resistor R40 to run hot because of excess current draw. The 12BY7 has negative bias supplied to its control grid, enough to cut it off during receive with the bias reduced in transmit so that the driver is operating in class A.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 2:17 pm 
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Thanks Rodger. I could have gotten hold of the wrong pin. I'll get a bright light and verify all the pin voltages.thanks for all the help.

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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 5:20 pm 
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A 3 looks a lot like a 5 on a socket buried deep in a radio so it would be an easy mistake to make!

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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 9:05 pm 
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Ok , not sure how many more times i can turn this thing before it really gets bad. Haha. Something really stinks. Smells like burnt wire.
Anyway here is what i have on the pins of the 6js6c tubes
1 .1 mv
2 0 v
3 +176 vdc
5 +315 volts dc.

Looks like something is bad wrong.

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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 9:10 pm 
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One more thing the bias adjust on thevoltage regulator card was very warm.
Thanks

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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 10:09 pm 
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Pull the tubes out for additional voltage testing, they don't need to be in place. That should help prevent collateral damage.

I am not coming up with any good explanation for that voltage on the tube pins but clearly something is seriously wrong with the power supply situation or there is a wiring error in the set. Are there signs of previous repair in the power supply and regulator sections? Were there tubes in the set when you got it? Maybe someone was rewiring for a different tube type.

Rodger WQ9E


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 Post subject: Re: Yeasu 101
PostPosted: Jun Thu 14, 2018 10:24 pm 
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Yes the original tubes toshiba green stripe 6js6c were in place, and it worked for about a hour before this started. I checked the voltages off regulator board and the only one that was way out was the -100 . It was -170. Dont see any repairs made, it looks like someone just set it aside for 40 years. Does the driver supply bias voltage for the operation of the finals ? Where in hell did the 360 volts come from.

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