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HT-32A Blew a fuse	Reply
by KB2FCV on October 8, 2008	Mail this to a friend!
Hi everyone. I was using my HT-32A the other day and it popped the fuse. I simply had it in the CAL position so that I could zero beat the transmitter to the receiver. There was no curl of smoke, no sound.. it just powered off and blew the fuse. I'm not that great at debugging stuff, I was wondering where I should start looking? I am guessing start in the power supply circuitry and work my way in? I haven't replaced the fuse or powered it on since it happened.. as I want to check everything out first and find out why it popped. I'd hate to burn up a transformer for something like a capacitor going. I didn't notice anything at all strange before that.. the transmitter was working just fine. 73, James KB2FCV

RE: HT-32A Blew a fuse	Reply
by AD4U on October 8, 2008	Mail this to a friend!
If you were comfortable making some basic checks with a VOM I would recommend that you do just that. But since you said something in your post to the effect that you are not the best trouble shooter, I would suggest this. This rig is over 40 years old. Perhaps the fuse is original and maybe it just got tired from many on-off cycles. Since you are not comfortable trouble shooting the rig, I would install a new fuse of the proper rating and try again. If the fuse blows a second time, stop and call for help. I really doubt if you will hurt the rig by trying another fuse. If the new fuse does not blow, operate the rig and have fun. Dick AD4U

RE: HT-32A Blew a fuse	Reply
by KA5N on October 8, 2008	Mail this to a friend!
A simple trick I use is to look at the blown fuse (only works with glass fuses)and see if the element is parted and there is no discoloration of the glass inside. If the glass is clear then the fuse may have failed mechanically and there is no short. If there is black soot on the inside of the glass, be assured that a REAL short occurred. In short if the glass is clean, try a new fuse if it is black do Ohmeter checks first. Shorts don't often heal themselves and if you power up with a short you may damage something expensive. Allen

RE: HT-32A Blew a fuse	Reply
by W5RKL on October 8, 2008	Mail this to a friend!
If the new fuse blows, check low voltage power supply dual can filter capacitors C79A/B (60ufd and 40ufd at 475VDC). If one or both of these filter capacitors are shorted to ground internally due to age the fuse will blow. C79A/B is located directly behind the VFO. Also check negative supply filter capacitors C98 and C99, both 40ufd 150VDC. Also check C80 HV oil filled filter capacitor for oil leakage. C80 is located on the top right rear of the chassis. The schematic incorrectly labels this capacitor as "C50". Figure 7's picture on page 11 of the manual shows the physical location and label C80. If C80 is physically leaking, maybe slightly, fix the oil leak. 73 Mike W5RKL

RE: HT-32A Blew a fuse	Reply
by KB5ZXM on October 8, 2008	Mail this to a friend!
Do all your testing unplugged. There ARE Lethal Voltages, generated in this device. Exercise great caution, one hand behind your back when probing. Work Thou NOT on High Voltage Circuits while Energized, Lest, Thy friends by beers for thy widow, and console her in better days.

RE: HT-32A Blew a fuse	Reply
by KB2FCV on October 9, 2008	Mail this to a friend!
Hey guys, Thanks for all the replies, it sounds like I have some good direction to start. I've had tube gear a number of years so I understand and follow good safety measures when working on this gear. You can't be too careful! While cautious when working on this gear and good with a soldering iron, my 'debugging' and troubleshooting isn't that great.. still working on it. To answer a few questions - the fuse definitely is charred and black on the inside. It blew with authority. My first guess was probably a filter capacitor or some other capacitor finally decided 50 years is enough to 'retire'. I will check the suggested capacitors and then get back to everyone here. If that's the case it looks like I'll be placing an order for some capacitors. Probably not a bad idea anyways..

RE: HT-32A Blew a fuse	Reply
by K9EID on October 18, 2008	Mail this to a friend!
James: Sorry to hear of your Hallicrafter problem. Dick is on target about the fuses in these ole gals. Many times, they sometimes just get tired but if they are BLACK inside the glass....something is probably shorted in the supply. I have several of my original transmitters of the 50's and 60's still on the air. Harvy Wells, HT 37, 20A, KWM2A, etc. One of the things I feel that has 'saved' them is my Variac. ALL of the power switches are left on - never turn them OFF. The entire 'boatanchor' rack is wired to a Variac. As I enter the station I slowly raise the Variac to 110 volts - no more. Our power lines here typically run 126 to 130 volts which I feel is real torture to these babies that were designed for 110 volt a.c. inputs. I also feel the sudden 'THUD' when you snap that power switch on and off certainly doesn't help the life of those power supplies. Over the years, I have had several fuse 'malfunctions' and hope that this replacing your fuse heals all. Hope to catch you on the 14.292 Sunday afternoon 'Vintage SSB' net. BOB HEIL, K9EID

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