[Kenwood] Kenwood TS 520- Fuse blown

[Patrick A. Thompson Sr.]

Sounds like you need to study the power supply section.

The good thing about your problem is that it is definite and repeatable.

First review how to work around electric shock hazards.  Be sure the 
filter caps have discharged by measuring with a voltmeter and then 
taking them to ground as a precaution with a clip lead.

When you are sure there is no shock hazard (rig is unplugged from AC and 
the caps discharged), I'd check the HV power supply.  Measure each of 
the rectifier diodes. The diodes are on the rectifier unit shown on the 
overall schematic. I don't know how easy they can be accessed. If you 
are lucky you may find one or more shorted. If not diodes then check the 
electrolytic filter caps. They may have shorted. If you can see a short 
or low ohms to ground on the B+ line you then review the circuit and 
inspect components that might have shorted.  If you are lucky there will 
be some discoloring or heating.

In particular from Kenwood service notes:

check C31 100uf 500v for short

There may be some others on the list that have seen this particular 
fault.  Fortunately I haven't had to dig too deeply into my 520.

Pat
wa4tuk



GORDON MULLEN wrote:
> 
> 
> I recently purchased a Kenwood TS 520  and when I power it on the fuse 
> blows afer a couple of seconds.
> 
> I looked at the service notes and they mention possibility of chassis 
> short in circuit B+.  Could not find
> B1 in the Service manual.  Also mentioned a couple of transistors 
> causing the fuse to blow in the receiver circuit.
> 
> Has anyone had a similiar problem .   I thought that something may have 
> gotten jarred during shipment and plan to change the tubes.  Is it safe 
> to power it up with the tubes pulled?
> 
> Don't want to make things worse.
> 
> Thanks,
> Gordon Mullen
> KI4NEH
> 
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