12BY7A Driver board PB-1714A

The driver board amplifies the SSB/CW signal and feeds it to the PA. The driver uses a tube (12BY7A) for delivering the necessary power, and the tube is also used in the automatic level control circuit (ALC). Part of the output is available at a connector at the back, for use with transverters or other purposes. Tuning is done with the same inductive tuning unit, that is used by the RF board. The inductive tuning allows a constant output over a greater range. The heater of the tube is switched by the heater switch on the front. By using this switch during longer receiving-only periods, the tube will last much longer, and there is less heating up.

  Here's an interesting problem I spent the better part of the afternoon trying to find in a customers FT-101ZD.  I get the unit from the customer full of dirt hardly working and barely receiving.  Cleaned up the switches and controls and the unit started to receive, the transmitter was still dead in part due to resistors having been cut on the rectifier "B" unit PB-1968 by the last rocket scientist who tried to fix it.  After repairing the rect "B" unit and replacing several resistors we are ready for a test of the power supply. Plugged it up, turned it on and Poof smoke!  First I thought the filter capacitors were bad, so I pulled them out and the power supply smoked again with the caps out of the set.  Time to move further into the set. Removing the 300 volt line that goes further into the rig prevented the rect "B" unit from smoking.  Disconnecting wiring all the way back to the 12BY7 driver unit PB-1714 we could remove the problem and stop the unit from smoking. Taking a very good light and a good magnifying lens to the driver unit revealed nothing visible to the eye.  Hooked up the driver unit again and ~ poof more smoke back on the rect ":B" unit.  No choice but to pull the driver unit and try and figure out what is going on.  In the case of the FT-101ZD the 300 volt supply going to the driver unit feeds directly to the plate of the tube and pin #7 of the tube socket.  Sounds easy enough unless you're the one having to do the troubleshooting.  There was nothing there that would cause the power supply to keep burning up. SO ONE WOULD THINK.  Using an ohm meter on the circuit revealed a low resistance to ground, but there was really nothing on the driver unit PB-1092 that would have gone short, no capacitors mounted on the driver unit plate circuit to go bad. So I pulled the driver unit out of the transceiver and this is what I found.   A carbon track from Pin #7 directly to ground at the center of the tube. Spent a good part of the day looking for this one!  A replacement tube socket and a half hour later putting everything back together and we were up and running.  How can you ever be bored with ham radio as a hobby when you learn something every day. (W4CLM)

 

Beware of what lurks beneath your next purchase! In short "Breaker 19"

From the W4CLM vault of horror stories comes this one about an FT-101ZD that was used on eleven meter AM a bit too long! Almost hard to tell, it could have been the work of a .22 Cal bullet, but the sad fact of the matter is that excessive current and long periods of key down time can easily result in damage like this to any amateur transceiver that is used by a careless operator.  The mess in this rig also took out the main power supply transformer.  The rig was eventually repaired and put back into amateur service.

 

 

 

 

PAØPGA's FT-101ZD Internet purchase

The PA with 6146A and 6146B tube	The “skilfully repaired” PA	The creative relay solution and choke	The PA now, after reconstruction	The rebuilt PA with 6146A tubes

Hints and Kinks by PAØPGA

In this section I will give facts and thoughts, that I have collected from all over the net. When sources are known, I will mention them, because to hold your FT-101ZD in an excellent condition is only possible when all real amateurs, share their knowledge and experiences. That’s still the first rule for a Ham in my opinion. Of course are all tips free to use, but using them is always at your own risk. If you don’t have the knowledge or technical skill, then please let the lids of your set closed, it is always better to have a good working transceiver then a perfect heap of junk. Never try to be smarter than the HF engineers of the design Lab, there is almost always a good reason that things are done the way it is. Most modifications are small, and are additions for a specific reason, not a complete rebuild of the set. So have said that, we start with a collection of tips:

First mixer overload (only FT-101ZD MK2 and MK3, board PB-2154, used after run 17xxxx,) RF board: Improve the dynamic range of the first mixer by modifying the T-Pad attenuator on the input as follows: Change R8 (120R) to 36R, change R9 and R10 (10R) to 27R. Reset overall gain on IF board using VR02, which is the source load of Q15. Source: G3TJP

Tips from "ZL" Kiwi land, On 10 meters the transmitter takes off on HF or with the transverter being used. The problem is poor solder connections and ground points around the 12BY7. Resolder all connections on and around the 12BY7 board. Source: ZL3MH