[Premium-Rx] Fwd: WJ 8888 noise floor problem

[Peter Rovardi]

Sent from my iPhone

Begin forwarded message:

> From: Peter Rovardi <peter.rovardi at btinternet.com>
> Date: 8 July 2015 15:52:10 BST
> To: premium-rx at mailman.qth
> Subject: Re: [Premium-Rx] WJ 8888 noise floor problem
> 
> Hello,
> My 8888A was working fine for the last 18 yrs ( new battery fitted 5 yrs ago) until the 1st LO developed a fault recently. This I managed to cure after many hours however it has now developed another fault! 
> This is best explained as a gradual increase in noise floor over a period of some 20 to 30 minutes, from cold switch on, resulting in  total masking of received signals!
> I have used lots of "freeze it" component cooler trying to locate this weird fault but to no avail.
> Wonder if any other 8888 fan in the group could possibily advise on this problem? 
> Not sure what WJ quoted as the MTBF for the 8888 was, but bet it was a lot less than 40 yrs!
> Thanks &
> 73 to all,
> 
> Peter Rovardi. G4HSB.
> 
> 
> 
> Sent from my iPhone
> 
>> On 4 Jul 2015, at 03:53, Heinz Breuer <hbreuer at debitel.net> wrote:
>> 
>> Hello Glenn,
>> thanks for your message.
>> I will check the battery first thing in the morning.
>> I downloaded the manual and it seems that the battery is on A22 board behind the front panel.
>> Do you know of a suitable replacement for the battery?
>> vy 73 Heinz DH2FA, KM5VT
>> 
>> Von meinem iPhone gesendet
>> 
>>> Am 04.07.2015 um 00:26 schrieb Glenn Little WB4UIV <glennmaillist at bellsouth.net>:
>>> 
>>> Has the NiCad battery leaked?
>>> 
>>> A leaking battery has all but destroyed two 8888B receivers here.
>>> 
>>> 73
>>> Glenn
>>> WB4UIV
>>> 
>>> At 04:38 PM 7/3/2015, Heinz Breuer wrote:
>>>> Hello,
>>>> I bought a Watkins-Johnson WJ 8888-2 receiver last weekend at the HAMRADIO fair in Friedrichshafen/Germany at Lake Constance. The seller assured me that the receiver was working fine and I have no reason to doubt it. Anyhow I put it up today and there is a faulty synthesizer.
>>>> 
>>>> I listend to a cw station at 7,021.80 with the 500 Hz filter. When I slowly turned the vfo knop upwards the cw pitch changed as expected. When I reached 7,022.00 there was no change up to 7,029.99. Obviously the actual receive frequency did not change between 7,022.00 and 7.029.99
>>>> I noticed the same with an SSB station at 7,191.80. The receive frequency didn't change between 7,192.00 and 7,199.99
>>>> Receiving condition were very poor today and I didn't have much time to evaluate the fault any further but it seems that this fault exists every 10kHz at all freuencies xx,xx2.00 to xx,xx9.99
>>>> 
>>>> As a first step I pulled every pc board one by one and put it back in but it didn't help.
>>>> 
>>>> I have not yet downloaded the manual and schematics. This will be the next step. I am well aware that the receiver is almost 40 years old. I know that it has tantalum capacitors which are prone to failure.
>>>> 
>>>> If anybody experienced a similar fault I would appreciate any hint where I should start looking.
>>>> 
>>>> Thanks in advance for any help.
>>>> 
>>>> vy 73 Heinz DH2FA, KM5VT
>>>> ______________________________________________________________
>>>> Premium-Rx mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/premium-rx
>>>> Help Page: http://mailman.qth.net/mmfaq.htm