Text with *** from Bob Pease, in response to Roy Johnson

At 04:50 AM 7/26/2009, Roy wrote:


Very many thanks for sharing the personal and Philbrick sites.

I have spent a long time admiring them and realise many shared interests.

I have always been a fan of Gas tubes since designing a dekatron and gas thyratron counter in the early 1950s for a radiation meter.  They may well be capable of further development which was truncated by the coming of the transistor.

My "association" with Philbrick dates from the early 1960s in the U.K. where I was using operational elements to process signals in aerodynamic turbulence research.    Initially the modules were tube (valve) devices and the  applications simple - such as integration over several minutes using dekatron counters and relays.  Subsequently squaring, multiplication and correlation  functions were developed.

Before Teledyne-Philbrick established their own office in the UK, the agents were A.E.P. International. Both offices were close to Heathrow airport.  The module documentation and application notes were excellent and I still have some from that period.

My collection of Teledyne-Philbrick-Nexus modules includes






FLA-1 (Nexus)

SA-1 (Nexus)

SQ-10a  (Nexus)

At first the only real competitors in the solid state area were Analog Devices and Burr-Brown, but UK companies quickly started to match some of their performances.   Ancom, Computing Techniques and Amplicon produced some good items before integrated circuits were developed.

I have not tested any modules recently - it would be interesting to know how they perform after 40 years.  Were electrolytic capacitors used?  One would need to bring up the voltage current-limited slowly,  before full voltage application.  Perhaps when I get time ................

Thanks again for telling me of your excellent sites,

Best regards,


On Jul 27, 2009, at 9:25 PM, Joe Sousa wrote:


Interesting to hear your experience with Philbrick and other contemporary engineering efforts. 

I don't remember seeing electrolytic caps in solid state modules. Perhaps Bob Pease, who designed some of them remembers. Dan Sheingold or Alan Risley may also remember.



From: Robert Pease [mailto:czar44 AT me DOT com] 

Sent: 28 July 2009 07:24

To: Joe Sousa

Cc: Roy AT mendit.org; Sheingold, Dan; Alan Risley; Robert Pease

Subject: Re: Caps in Philbrick modules

   *** Hello,  Friends, 

  I don't normally like to add one paragraph  on top of  20,  so I'll do this just once:

Philbrick and  Nexus usually put in 0.01  UF  P.S. bypass caps, in potted  modules.  They were generally  reliable. We rarely had any problems;  nor our customers. 

We rarely even recommended 2.2 or  10 or 22 UF as bypasses, NEAR  the op-amps.  Maybe  the  customers  figured out  for themselves, to do this, in critical places?   I bet the P45 needed some  2 UF or more.  But I wrote the datasheet, and  I don't recall mentioning it.  I  haven't got a P45 or PP45  datasheet near by.

The SP656  had a 330 UF  Sprague 150D  tantalum, in the main chopper filter;  but that was rare. Most other modules, potted,  or  not  ( P or SP)  had no electrolytics or tantalums.

Best  regards. /  rap 


 OH  YEAH:   The  4701  VFC  had a 3.3 UF  tantalum on the "summing point", as the main integration filter; but it never got any transients. It was protected and limited  to  1 volt or 1 mA.  The 4705 or 7 or 9 had no electrolytics.

The 4702  FVC  had a 1 UF as a little  filter,  near the output's summingpoint, and it, too was well protected. We  _NEVER_  had  problems  with those. 

 All I can think of. / rap 

Cc: Robert Pease <czar44 AT me DOT com>, k2w AT philbrickarchive.org

From: Robert Pease <czar44 AT me DOT com>

To: Roy 

Subject: Re: Caps in Philbrick modules

Date: Tue, 28 Jul 2009 20:38:07 -0700

On Jul 28, 2009, at 12:24 AM, Roy wrote:

Dear Dr Pease,

Many thanks for the rapid and helpful response.

 I'll have to wind some of the modules up when I get a chance - I bet that they will be fine!


 *** No  doubt. 


Tant caps have had a bad press, but I suspect that comes more from the radio experience than the industrial areas where I can only recall seeing one failure in a psu. 


 *** Some of the bad press on  Tantalums  came  from people  buying the  CHEAPEST available  caps.  We  didn't do that.   At Philbrick, we  bought almost  entirely from Sprague. 

*** Some of the bad press  ALSO comes  from having a tantalum  across thePS Busses  when power is switched on  FAST.  Apparently the fast turn-on transients are bad  for Tan Caps  if there is no series R  to limit the I.   Mil-Specs  say you need  to put in the R.


As a matter of principle I always added a few uF and a 0.1 close to the socket.   

Never does harm - may do good.

 Many thanks for your comments  (and for the excellent designs!)


  *** Have  fun! /  Best wishes. /  rap 


 Best regards,



P.S.  Thanks, Joe, too for your response.