ser #1917 800b fm trouble

[john stafford]

i am new to Scott a well built unit but complicated

my problem is the FM, the am & shortwave work.my problem is in the v17 tube c-75 c79 caps leak badly my unit has a 3 connector bathtub cap of .05 mf at c75 the print has only 2 lugs the cap i have has a common lug not on print, can any one tell me the purpose of the common is it ground and can it be removed

 FM is 0 sound  and no movement of the FM eye

i have signal tone at v17 pin 8 and tube v18 to speaker the v17 tube circuit  has me confused for some reason hope you can help .......      A update still working on FM i ck tube 6sj7 v-17 tube the resistors on pin6 should be 11,600 ohms i get 54k and i count find out where it is coming from any thoughts

thanks

john

PS. FM working fine just have to plug in the cable!!!!! just one of toughs days

[Keith Lowe]

John, the bathtub case is the common ground on both of those cans.  I had two brands of bathtub condensors on my Scott.  The ones that have American Condenser stamped on the cover are wax filled and everyone one of mine was leaky.  The ones that do not have a name stamped on the cover were oil filled and these all tested ok on my Scott.  Norman is the expert on 800B's and I suspect he'll reply soon.

[john stafford]

it is just confusing that out of all of the bathtub caps the only 3 or so would have a 3rd lug for internal ground is their any other use then ground

john

[john stafford]

thank you keith for your help

john stafford said:

it is just confusing that out of all of the bathtub caps the only 3 or so would have a 3rd lug for internal ground is their any other use then ground

john

[Keith Lowe]

John, was your common lug not connected?  I'd go with the schematic and connect it to ground.  However, I'm the least experienced of member of the forum and I'd wait for one of the experts to chime in.

Keith

[john stafford]

i went over the photos i took of the v17 c-75 show 2 resistors on the c lug and both go to ground,the problem i have is why do some of the caps have a extra lug for ground instead of using the hold down tab as ground some one knows out their in radio land

[José Bustos]

Hello John:

My 800B has the same C75 bathtube cap with 3 connectors.

I reccapped it with two .05mf new caps soldering one leg of each one to the third connector. Outside of the bathtube that connector is soldered to ground, originally.

 

I do not know why Scott used one of 3 connectors instead of two.

 

By the way, the FM is working but the magic eye moves just a few. Perhaps is a matter of alignment. I am working on that.

 

I will measure the point to point resistance terminal to chassis for 6sj7, v-17 and I let you know the values.

 

Kind regards,

 

José

 

 

 

[José Bustos]

John:

First of all, I changed all the resistors on this radio, included those inside the RF and IF cans. They are new ones, Many of the old ones were out of value.

 

My V-16 and V-17 are new also.

 

For FM and AM I have the same values on V-17, that is to say:

Pin 3 and 5: 0 ohm

Pin 4: 41,3Kohm

Pin 6: 14,8Kohm

Pin 8: 149Kohm

 

All this measurements are closed to AM values showed  on page 15-60 Scott on Rider's manual.

 

It is strange, I have same values for FM and AM, but like I said, the FM is working. My only problem is the no sensitive magic eye.

 

You get 54Kohm on pin6. Is the R73 resistor close to 15Kohm?  

 

Kind regards,

 

José

[john stafford]

thanks for the help i replaced the res on 6 so its now 15k but i have v15 pin 4 27k should be 56 ohms andv16 pin 4 50k instead of 27ohms i have removed the cans and ck res and caps they seem to be ok so i am at a lose i still have good signal at v17 pin 8 plate very strong pin 4 1/2 of 8 but clear nothing on 16-15-so onfrom v17 to spk ok i think my brain died for some reason i can not see where the prob is, i have replaced many bad rest and caps all of the bathtubs many restuffed i have not worked on to many FM units so any help would be great

john