Re: Two Ampliphone HV problem questions

Ok good to know that an analogue meter will do the job (although I don't have one). I think you are right John, I think that was what he explained.

Still: pretty strange that yours reached 27kV, Mark claimed the Cinelabs were designed to never reach that value AFAIR. A service bulletin from Atari later instructed to turn the protection value all the way back because often it was kicking in while it hadn't actually reached dangerous levers. Did you measure the HV without any signal on the inputs, because that is what the manual says to do.

Verstuurd vanaf mijn iPad

> Op 17 feb. 2014 om 04:47 heeft "David Shoemaker" <davids@oz.net> het volgende geschreven:
>
> Borrowed an analog meter and get a nice solid 6.3vac at the heater
> connection on the board. So I apparently spent two days chasing a ghost :)
>
> Turned it on again without my shop light pointing into the back and noticed
> the heater light for just a moment and then it went out and the HV cutoff
> LED came on. I hadn't noticed that before so got out the HV probe.
>
> 27Kv... Uh, well there's your problem :)
>
> Did the HV adjustment procedure (both pots had been maxed by someone before
> the board came to me for service) and now have a stable picture with 19.5Kv.
>
> So #1 is all better.
>
> Any ideas on #2? I guess I need to finish building my flyback ringer so I
> can test that.
>
> David
>
> -----Original Message-----
> From: owner-vectorlist@vectorlist.org
> [mailto:owner-vectorlist@vectorlist.org] On Behalf Of John Robertson
> Sent: Sunday, February 16, 2014 5:30 PM
> To: vectorlist@vectorlist.org
> Subject: Re: VECTOR: Two Ampliphone HV problem questions
>
>> On 02/16/2014 12:21 PM, Andre Huijts wrote:
>> I think Mark from Cinelabs once explained why the heater voltage can't be
> really measured correctly with a DVM but I forgot the reasoning why.
>
> I would think that considering it is 20khz AC for the filament that
> meters may have trouble measuring that value - the diodes to rectify the
> incoming AC to take the DC voltage may not be fast enough...
>
> Thus one can expect the AC voltages to be difficult to measure with
> anything less than a 'scope and a small load on the AC heater line to
> stablize it.
>
> If the transformer is putting out correct rectifier DC then the filament
> voltage should be fine.
>
> John :-#)#
>>
>> Verstuurd vanaf mijn iPad
>>
>>> Op 16 feb. 2014 om 08:12 heeft pj pj <pj1@shaw.ca> het volgende
> geschreven:
>>>
>>> The Cinelabs transformer uses the (white) wire wrapped a few times around
> the ferrite as the winding for the filament voltage.
>>>
>>> One side goes to the HV board directly, the other via a resistor in
> series. Start tracing from the socket to back to that winding.
>>>
>>> The tube if I remember correctly needs 6.3V for the filament, so it
> sounds like something is running open circuit.
>>>
>>> Hope this helps.
> ---------------------------------------------------------------------------
>>> ** Unsubscribe, subscribe, or view the archives at
> http://www.vectorlist.org
>>> ** Please direct other questions, comments, or problems to
> chris@westnet.com
> ---------------------------------------------------------------------------
>> ** Unsubscribe, subscribe, or view the archives at
> http://www.vectorlist.org
>> ** Please direct other questions, comments, or problems to
> chris@westnet.com
>
>
> --
> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
> Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
> www.flippers.com
> "Old pinballers never die, they just flip out"
>
> ---------------------------------------------------------------------------
> ** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
> ** Please direct other questions, comments, or problems to chris@westnet.com
>
> ---------------------------------------------------------------------------
> ** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
> ** Please direct other questions, comments, or problems to chris@westnet.com

---------------------------------------------------------------------------
** Unsubscribe, subscribe, or view the archives at http://www.vectorlist.org
** Please direct other questions, comments, or problems to chris@westnet.com
Received on Mon Feb 17 05:13:43 2014