Modified Farm Radio

View previous topic View next topic Go down

Modified Farm Radio

Post by 35Z5 on Sun Apr 20, 2014 10:04 pm

This is something I've been threatening to do since I got this Mantola farm radio seven or eight years ago... I'd like to use it as a occasional player, but the puny 3Q5 audio always irritated me so I'd cut it off in a few minutes... Since it had it's fair share of crumbling rubber wiring, I'd already totally removed the AC/battery switch and associated wiring, so figured it's now or never(well about three weeks later)...



This Truetone D1123 is close to my radio, I've never found the exact schematic for the Mantola 672 version, used a rotary switch for AC/battery select instead of cord plug...



After I finished the dirty work this is the circuitry, ARF member bikenswim suggested the filament circuit as used in a Emerson 505 portable... I'd been considering a 25Z6 to power 50L6(25L6) and filaments seperatly as a 35Z5 would be at the max current limit operating both... This method more or less gives a free 50ma to operate filaments... The 50L6, OPT & 8" speaker were mostly donated by the remains of a 1952 Zenith radio/phono(phono had been sawed off)... Original speaker was 6" mounted on a reducer board..Results are very noticeable, should have modified it sooner...

I had to get creative with marrying the schematics as my program isn't interested in coping from a outside source... .

avatar
35Z5
Member
Member

Number of posts : 461
Registration date : 2008-03-12

Back to top Go down

Re: Modified Farm Radio

Post by harold wright on Wed May 14, 2014 9:26 pm

Nice work, 35Z5.

Harold

harold wright
Member
Member

Number of posts : 51
Registration date : 2012-10-14

Back to top Go down

Re: Modified Farm Radio

Post by 75X11 on Thu May 15, 2014 6:58 am

You do nice work! Sorry For my late notice, my new job keeps me from noticing these things as soon as I should.
avatar
75X11
Member
Member

Number of posts : 4900
Age : 60
Registration date : 2013-03-10

Back to top Go down

Re: Modified Farm Radio

Post by 35Z5 on Fri May 16, 2014 8:45 pm

'ppreciate it...

I did go back and added a fixed tone control circuit that's nothing more than a .002 & 150K resistor in series to ground off control grid(pin 5) of 50L6... Even with the increased output, was still a bit sharp sounding so I tried various resistances from the substitution box till I liked the tone... With a variable control, usually there is a 500K to maybe 1 meg control in series with the .002...

I've also added a pair of #159 wedge base dial lamps(same spec as 47) at either end of dial scale, it now glows in the dark... For those I used a small power transformer pirated from a junk solid state radio...



I secured the wiring after the shot...

avatar
35Z5
Member
Member

Number of posts : 461
Registration date : 2008-03-12

Back to top Go down

Re: Modified Farm Radio

Post by Marco-ni on Sat May 17, 2014 8:54 am

Nice, really nice 35Z5
avatar
Marco-ni
Member
Member

Number of posts : 42
Registration date : 2014-03-31

Back to top Go down

Re: Modified Farm Radio

Post by Sponsored content


Sponsored content


Back to top Go down

View previous topic View next topic Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum