[Heath] The DX-60B Issue - Lamp in series with the 120VAC

[Paul Robinson]

All:

I do not apply full power to an old rig.  It is not necessary and can do 
a lot of damage.

I like installing a 60 watt or 120 watt (120VAC) incandescent lamp in 
series with the input power.  This limits the 120VAC current to 1 or 2 
amps and prevents a lot of smoke.
It also allows one to take some measurements.  I have been known to 
short the load with a clip lead (the DX-60 in this case) when the power 
is tuned on, then when the lamp is lit, I remove the load short.  In 
this way there is no surge to the load when the power is applied to the 
load.  The load sees a nice constant current 1 or 2 amps.

I have also installed a switched AC outlet and an isolation transformer, 
at my bench, which I use during these times.

Something to think about.

ALSO:
Old rigs have aluminum electrolytic capacitors which need to be slowly 
powered up (re polarized, I think is the term) as the leakage current 
through the capacitors will be high when power is first applied.  A 
variable transformer will allow the power to be increased slowly over a 
10 hour or 24 hour period and this seems to work.  Again, I use a 60 
watt or 120 watt (120VAC) incandescent lamp in series with the input 
power which will limit the current if something drastic happens during 
this process.

If you are not qualified or experienced to work on this equipment then 
do not.

Later,
Paul
VE1AVD


-------- Forwarded Message --------
Subject: 	Re: [Heath] The DX-60B Issue
Date: 	Sun, 01 Apr 2018 21:52:38 -0700
From: 	Kenneth G. Gordon <kgordon2006 at frontier.com>
To: 	Doug & Kathy Davies <dkdavies3 at gmail.com>
CC: 	Heath at puck.nether.net




On 4/2/2018 11:52 AM, Kenneth G. Gordon wrote:
> On 31 Mar 2018 at 16:09, Doug & Kathy Davies wrote:
>
>> testing.  When I plugged it in, all seemed ok i.e all the tube filaments lit up and nothing smoked.
>> Then, I put the Function Switch in TUNE and got a loud hum from the transformer and I let the
>> smoke out of resistor R35.  I re-checked everything and found that resistor R34 was open.
> The loud hum from the power transformer indicates that your +HV is dead-shorted
> somewhere. Either there was a wiring error or a component had failed or was installed
> incorrectly.
>
> For instance, if you had inadvertently connected C-39 and C-43 in revese, they would show
> a dead short to ground.
>   
>> Now I don't know if R34 was open prior to R35 burning up.  I didn't check component values prior
>> to testing.  The question then is, did R34 open as a result of R35 smoking or was it open prior to
>> that event?
> >From the sound of things, both burnt up at the same time. If R-34 was open, all that would 
> do is prevent the plate-voltage (~ 700 VDC) from reaching the final amp plate.
>
>>    I would think that if R34 was open prior to testing, it would certainly put a huge strain
>> on R35 causing it to burn out.  Am I correct here?
> No. The two resistors are in separate parts of the circuit: if one failed, that would have zero
> bearing on the other one.
>
>>    Going over the circuit, I can't see anything
>> else that would have caused R35 to smoke.  Any ideas?
> You have a dead-short to ground at the 700 VDC output lead of your power supply.
>
> Is C-19 shorted?
>
> As another fellow mentioned, be EXTREMELY CAREFUL HERE: THAT VOLTAGE IS
> LETHAL!!!!!
>
> Ken W7EKB
>
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