Tempo One squealing

[KD7VEA]

OK, so I stumbled across a tempo one at a yard sale a while back, and figured I would pick it up to send out to a ham friend in Texas. The radio seemed to work well at first, but I have started noticing it is getting harder to tune. Sometimes I can get it to produce a full 100-110 watts out, and other times, maybe around 60 watts. I follow the same tuning method every time, and the bias is adjusted to 60mills. Now keep in mind that I am not a tube guy, I grabbed this radio because the price was too good to pass up. The real problem I am having is that I will tune it up, and if I key the radio for maybe 30 seconds or so and start calling a string of CQs, the needle starts to drop, and the power drops to no output. At this point there is kind of a squealing noise coming from the speaker, no RX, the meter is pegged at full scale, and no output. What would be the likely cause of this issue? I was wondering if the tubes were starting to go bad. I can occasionally hear some slight arching(sounds like inside the tubes) when tuning. any ideas? I am trying to get this running so I can ship it out to my friend in Texas, and I am just hoping it is not going to cost a fortune.
Jake
KD7VEA

[KB4QAA]

Sounds like a microphonic oscillation, perhaps due to low voltage. I would start by checking the power section, particularly the diodes and caps. If they aren't obviously recent vintage, replace them. The smart thing would be to replace all old electrolytic caps.

[AD4DQ]

Yes, start with replacing any old electrolytics, I have a HW-100 that 1 bad cap prevented it from going into transmit, also check all tubes on a tube tester.....might as well. Those are the first things to do when buying an old tube rig.

[AF6LJ]

There are a numjber of causes and just blindly replacing parts isn't a good approach.
The best course of action would be to find someone who is experienced at working on tube gear.
This doesn't sound like a power supply problem..
Could be as simple as cleaning the band and function switches.

[KE3WD]

Do not replace a single component, do not tweak any calibration adjustment until you have first cleaned and lubed all controls and switches!

Dried out or dirty switch contacts are likely all thats wrong with it...


73

[KD7VEA]

Thanks guys, I did take the covers off when I first got the radio, and I blew out a lot of dust(a lot, like 50 years worth) so maybe I need to get back in it and really make sure that nothing else settled in the radio. Ill start there, because the problem is intermittent, I can sometimes get it to tune up and talk on it for a few minutes, so dirty contacts does make sense. Ill let you guys know what happens.
Jake
KD7VEA

[AD4DQ]

Yes, when you buy and bring home a old tube rig you just don't plug it in, turn it on and hope it works. What I do is take the covers off, check all tubes, clean all switches and contacts, inspect all wires and solder joints, then if the electrolytic caps are old and the originals I replace them, if they look newer and have been replaced in the near past I check them on my cap meter. The electrolytics are the only part I replace when I see they are old antiques. I agree don't just jump in replacing parts blindly for no reason. When you feel comfortable after checking everything then plug her in and see what happens. Then the troubleshooting begins.... well hopefully not. Good luck

[KE3WD]

Thanks guys, I did take the covers off when I first got the radio, and I blew out a lot of dust(a lot, like 50 years worth) so maybe I need to get back in it and really make sure that nothing else settled in the radio. Ill start there, because the problem is intermittent, I can sometimes get it to tune up and talk on it for a few minutes, so dirty contacts does make sense. Ill let you guys know what happens.
Jake
KD7VEA

DEOXIT spray. Very small amounts, directed at only switch contacts, don't drench things, won't help and in some cases may cause other probs.

DO NOT SPRAY AC POWER SWITCHES. That usually kills the switch rapidly. The power switch doesn't need the spray because the potential of the AC voltage can get through contact corrosion anyway.


73

[KD8GFY]

This FT-200 / Tempo One group, has many folks that are well versed on this radio and are happy to give sound advice. http://groups.yahoo.com/group/FT-200/

[AF6LJ]

This FT-200 / Tempo One group, has many folks that are well versed on this radio and are happy to give sound advice. http://groups.yahoo.com/group/FT-200/

This is a good place for information.