L17,L25 HI VOLTAGE FILTER CHOKE

[john stafford]

can any gents I.D  on a 800b power supply choke on one unit of the  2 chokes 1" apart and another two choke are next to each other. can you tell me the latest or did they use then both at the same time

thank you

john

[Norman S Braithwaite]

Initially the 800B power amplifier was designed and manufactured with a single choke.  According to service data this included chassis with serial numbers up to 2000.  Hum was a problem in the 800B therefore Scott Radio Laboratories added an additional choke during the production run.  The real problem source of hum, however, was the tone control circuit of which modifications are posted on this venue.  The later 800B sets were manufactured with two chokes spaced approximately 3/4-inch apart.  At the same time Scott Radio Laboratories provided instructions to install an additional choke on the earlier chassis.  Given the arrangement of components on the earlier chassis, the additional choke had to be mounted flush with the existing choke.  Therefore if you have an 800B amplifier with two chokes abutted against each other, you have an early version with an added choke to reduce hum.

Norman

[john stafford]

thank you for the info so the chokes with the 3/4" space are later the the close choke i am going to keep one of them. are the later unit a better keeper of the basicly the same

john

[Norman S Braithwaite]

I would not consider either version better than the other.  Please be aware that they are not completely compatible.  The FM signal plug differed between the two versions.

[john stafford]

are you talking about the fm plug with the single pin as to the 2 pin of later after june 25 is their a differance between the 2 pin units they look the same, i have a early model single pin i just finished  and 4 2 pins units hope this makes since

thanks for your help i can copy anything i am not so good with electronic i get by

john

[Norman S Braithwaite]

Yes.  The early version used the single pin plug and the later version used the two pin plug.  The electrical differences are minor but the plug or socket must be changed if mixing versions of the tuner chassis with the power amplifier chassis.

[john stafford]

norman old smart one

is their a way to tell the year of power supplys i have 5 PS only 1 has single pin but now with your info on the filters well help

is their a diff in the two pin units other then the speakers and p.s

thank you u are a great help..... now to help me do a alignment for some reason i am very nervous about doing it i have all of the equiment to do it............ just no guts to try it mybe a beer would help

john

[Norman S Braithwaite]

All 800B chassis were made between February 1946 and July 1947 and most were stored for later sale. I am sure that the early version power amplifiers were all made early in 1946. Other than that, there is no way to determine when the power amplifier was manufactured. The most significant difference between the versions is the way current is supplied to the motor tuning mechanism on the tuner chassis. The earlier version provided power directly through push-button switch contacts and the later version provided power through relays activated by the push-buttons. Apparently the tuning motor current was a little much for the push button switch contacts. These changes were all on the tuner chassis.

[john stafford]

from your info you hace been diong this for a while have you thought of writing a book, i thank it would help before a 4 yrs ago i never heard of scott i have 4 philco's from 32-46 and they were very easy to work on unlike the scott not only are they heavyest radio but more things to fix for a guy who pushing 80 yrs it takes all my brain power to repair then so thanks for your help it makes a old guy life a little easyer

john