The PHILCO Phorum
marconi 157 - Printable Version

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RE: marconi 157 - morzh - 11-21-2016

Well....I won't be able to tell from the pictures but the idea is, the cap C30 through R13 and the connected part of the switch should have the plate voltage for that pin 6. So see if it is there.

RE: marconi 157 - sam - 11-21-2016

hey picker
have you watched jornone on you tube
https://www.youtube.com/user/joernone/videos
john is great for beginner's to experts
if your adding wire to a cap to make longer. add wire first then tubing to cover and do a pig tail at end
makes it much neater
as far as coil wire .
wire most likely pull out of case just follow up and around to top.
it should go inside tube and up to one of the post

sam

RE: marconi 157 - the picker - 11-21-2016

(11-21-2016, 07:46 AM)morzh Wrote:  Well....I won't be able to tell from the pictures but the idea is, the cap C30 through R13 and the connected part of the switch should have the plate voltage for that pin 6. So see if it is there.
sorry for this question but where is r-13 connected

RE: marconi 157 - sam - 11-21-2016

heres more info
[Image: https://image.jimcdn.com/app/cms/image/transf/none/path/sf831be4bed1b452f/image/if911952454f6abe2/version/1391468879/image.jpg]

and 1/4 way down page some info
http://lrc-metro-maquette.jimdo.com/radio-antique-marconi-service-manual-1-plan-antique-radio-service-manual-marconi-1-plan/

RE: marconi 157 - the picker - 11-21-2016

thanks sam found it and replaced r-13 with a 56 k resistor and now have 90 dc v on pin 6 of tube 6k8 but still got the motor boating

RE: marconi 157 - the picker - 11-21-2016

also looking for c-24 and can not find it on the schematic

RE: marconi 157 - the picker - 11-21-2016

(11-21-2016, 01:12 PM)sam Wrote:  heres more info
[Image: https://image.jimcdn.com/app/cms/image/transf/none/path/sf831be4bed1b452f/image/if911952454f6abe2/version/1391468879/image.jpg]

and 1/4 way down page some info
http://lrc-metro-maquette.jimdo.com/radio-antique-marconi-service-manual-1-plan-antique-radio-service-manual-marconi-1-plan/
also sam I just noticed the cap list says c-19 is a .1 mfd but if you look at pacific tv schematics it says .01 mfd any idea which is right 

RE: marconi 157 - Arran - 11-22-2016

 That wire on the coil may be a what they called a "gimick" it's a home made low value capacitor, in any event it's on one of the short wave coils so it would not be responsible for the motor boating issue.
Regards
Arran

RE: marconi 157 - the picker - 11-22-2016

any help on the different cap value from the two different schematics

RE: marconi 157 - morzh - 11-22-2016

Picker

if you are looking for a part that is not in the sch (or seems to be) it helps to identify where it is connected and then look at the sch again. If it is not there.....there are various ways to figure out what it is and what the value should be.

RE: marconi 157 - the picker - 11-22-2016

hi I found cap 24 but still have a problem with cap 19 on the list in the forum it states that it is a .1 mfd but on pacific online schematics it states .01 mfd which is correct thanks

RE: marconi 157 - morzh - 11-22-2016

The sch says 0.01,uF. however 0.1uF will work just the same. Not important.

RE: marconi 157 - the picker - 11-23-2016

well I guess then I am back to the motor boating problem where do I look

RE: marconi 157 - morzh - 11-23-2016

Leaving 6F6 (output tube) in place start removing other tubes one by one and then putting them back.

First 6R7. Remove, see if the motorboating stops, then put back. If it did not stop, stop here.
If yes, then do the same with the 6U5 tube.
Until you find the tube where it does not stop with the removal (likely the RF tubes won't stop it).
Likely to be either of the 6U5 or 6R7.

Again, you have to find the last tube as far from the output (or as close to the antenna) that stops the motorboating once removed.

RE: marconi 157 - the picker - 11-23-2016

I first took the 6r7 tube out and it stopped and next the 6u5 and it did not stop so what to do next thanks