Clansman 353 Constant Whine

[TechnicianJack]

Hello,

 

I have recently purchased a Clansman 353 which arrived last Saturday. It appears to power up OK, however there is a constant loud whine from the back of the radio which occurs constantly from when the radio is switched on, to when it's switched off. At first I thought it may be the radio warming up, but after leaving it for a few minutes it remains unchanged. It is not fan noise as when I manually switch the fans on, they spool up, and then slow down and stop when switched off. The noise is not audio noise, as I disconnected the handset and it didn't stop.

 

The only thing I think may be an issue is the power supply I'm using for it. It's an old modified supply which outputs about 22/23V instead of a full 28V. (This was fine powering a DCCU to charge the manpack batteries) I'm not sure that the lower voltage would cause it to make that noise though. I also purchased a Clansman 321 which powered up with no strange noises on this supply.

 

Any advice would be appreciated.

 

Thanks,

 

Jack.

[g0ozs]

Jack

 

The 353 should operate down to about 20V and my experience with using it from batteries at 24-25V was that the squelch started opening intermittently as the battery got flat before it turned off but there was no whine. There is always a "chuntering" sound from the motor driven coarse tuning but I wouldn't call that a whine either. Do you get sensible readings "in the green" on the various meter switch positions - that will show up any major issues, but not necessarily something that works but is under stress - my guess would be that it is either an internal motor that isnt stopping or an issue with the inverter that generates the HT supplies for the front end and PA valves causing said inverter to squeal (much as some camera flash units do when charging). You will find that switchmode/inverter PSUs draw more current at low input voltage to achieve a given output power so that may be making it more noticeable. Noisy PSUs are usually due to loose transformers or coils acting as buzzers/loudspeakers and may require mechanical rather than electrical repair.

 

If it has a motor failing to stop I would be surprised if the PLL managed to lock - is the frequency readout backlight flashing ? If you have a frequency meter it may be worth checking that the output matches the dial setting within a KHz or so and is stable.

 

Unfortunately I am not aware of any full circuit diagrams for the 353 that have escaped into the Internet so you probably have to get hold of a spare set for parts and start swapping to do any meaningful diagnosis. Unlike anything else in the Clansman range it is a Valve/semiconductor hybrid and has significant high voltage hazards and large moving parts in the form of motorised turret tuners inside so great care is needed if it is powered up outside the case.

 

One other thing you can do is try it on different bands - the motorised turrets switch tuning components for high/low/mid bands so any problem specific to one band should be absent on the others - I think they are roughly 15MHz wide so if you test it at 30, 50 and 70MHz any different behaviour would be interesting !

 

The 321 draws significantly less current about 8-10 amps on full power CW TX versus 12-14 amps for a 353 at 50W - the RX power consumption is also much higher for the 353 than the 321 at about 4 amps.

 

Have you tried to key the transmitter into a dummy load yet ? That may show up more evidence - if PSU related I'd expect it to get a whole lot louder !

 

Regards

 

Iain

73 de G0OZS

[TechnicianJack]

Hi Iain,

 

Thanks for your reply.

 

I have borrowed a power supply from a friend which will output 28V at up to 10 amps and tested the radio on that. The voltage check setting puts the needle on the dial into the green, so that's OK. The radio still whines though.

 

I don't think it's a motor issue as you can hear the internal tuners spinning as you click through 10 MHz at a time from 30 - 70MHZ. The radio locks on frequency OK and and the dial stops flashing. One thing I've noticed is that the frequency won't lock if you tune above 75MHz. The motors slow to a stop, but the dial keeps flashing. While there's no usable Amateur frequencies in that range, I'm sure it should still tune to 79MHz?

 

I transmitted into a dummy load, and the whine stayed constant without any increases in volume. I only tested on the lowest power setting though.

 

Jack.

[g0ozs]

Jack

 

I will try one of mine at 79MHz and let you know if it locks

 

The min power setting is well under a watt so probably not much extra current than receive

 

Regards

 

Iain

[g0ozs]

Jack

 

I checked one of my 353s and the official user manual - the display flashes if the frequency is set to 76.000 or above and the June 1975 user guide gives the tuning range as 30.000 to 75.975

 

Regards

 

Iain

73 de G0OZS

[TechnicianJack]

Thanks for your help Iain. I've been in contact with the seller, and he's agreed to exchange the radio for me.