|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
28th Jan 2021, 3:58 pm | #41 |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
|
Re: Roberts R200 1st edition motorboating
Has the volume control been replaced? check the 47 ohm R21 it should be connected from secondary of output transformer to the earthy end of the volume control decoupled to chassis by r19 5.6 ohm. also make sure the other end of the secondary winding on the output transformer is taken to chassis
otherwise you have the a makings of a oscillator. John |
28th Jan 2021, 4:14 pm | #42 | |
Pentode
Join Date: Jan 2021
Location: Hinckley, Leicestershire, UK
Posts: 119
|
Re: Roberts R200 1st edition motorboating
Quote:
|
|
28th Jan 2021, 4:19 pm | #43 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Roberts R200 1st edition motorboating
R18 is not the problem, you measured it at 47 Ohms which is what it should be.
Lawrence. |
28th Jan 2021, 5:00 pm | #44 |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
|
Re: Roberts R200 1st edition motorboating
I think this radio has either been got at or is a cross between 1602 and 1449 trader circuits, it seems to have R14 and R15 in circuit (1449) with R21 and R19 (1602)if the volume control earthy end goes to + rail treat it as the 1449 early circuit with R18 being 220k, if the earthy end of volume control is via a 5.6 ohm resistor R19 then it is the 1602 later version with R21 being 47 ohms.
John |
28th Jan 2021, 5:11 pm | #45 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Roberts R200 1st edition motorboating
It's a production change that took place in the early version as set out in the service info, it gives the serial number starting from 27340 mentioning the 47 and 5.6 Ohm resistors and what else was altered etc etc.
Lawrence. |
1st Feb 2021, 12:15 pm | #46 |
Pentode
Join Date: Jan 2021
Location: Hinckley, Leicestershire, UK
Posts: 119
|
Re: Roberts R200 1st edition motorboating
All done, R18 at 220K.
Original handle, ends and locating bolts re-plated. Set of new brights, one was missing. Badge was broken, used one from a RD60. 2 coats of shoe cream. I did find that a 50/50 mix with pva glue primed any little scuffs, and covererd a little wear on the round corners. I will empty the Plessey caps and lightly glue them over the new ones, as it is looking a little empty in there. |
1st Feb 2021, 12:17 pm | #47 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Roberts R200 1st edition motorboating
|