early 30s Am Bosch 175 KC double-tracking issues

[Texasrocker]

Hello Guys, since this is primarily a Philco only website, I post questions in the B&G area sometimes, as I know many of us also service many other brands also.
I have completely electronically restored a early 30s (early-design-superhet attempt chassis) simple 5 tube AM/SW chassis. This radio-chassis had been previously *hacked* badly!! After full recap, and following JF Riders schemat, I have the set working again, and properly aligned according to JF Riders specs.
This radio is a AM/SW simple early design small tabletop chassis. Tube lineup: #2A7,# 58, #2A6,#2A5 audio, 80 rect. 3-gang tuner.
The chassis has 2 (screw-adjust) chassis-mount type oscillator-trimmers. According to the schem, one is for BC, the other for SW. Both trimmers share common gnd from factory. BC is strong reception, but SW is weak (but working also).
After carefully following "step by step" JF Riders alignment procedures, the radio is "double-tracking" strong local stations about 5Khz apart across the dial. (except for distant stations at night)
The BC oscillator screw- adjust, doesnt seem to change anything, however, by slightly turning the shortwave osc trimmer, affects the whole process of alignment. Im getting double-tracking on the BC band, but radio otherwise is working properly.
This radio is a Am Bosch model 350. IF= 175 KC ( I checked my RF gen against a Hewlett Packard digital freq counter, & also a digital crystal controlled portable radio receiver/ tuner for accuracy on 175 KC ( 4th harmonics on 700kc on the AM dial) RF gen was Spot on during alignment procedures for sure!!
Any suggestions why double-tracking is occuring? Randal

[exray]

First question...if you pass your sig gen thru the passband at IF do you see the double peak there?

[Texasrocker]

Hello Exray! This old 1933 model 5-tuber is a glorified TRF type chassis at best/ early simple design superhet attempt only ! (hee hee). No factory type loop antenna, outdoor longwire only connection. The antenna is fed directly to the bandswitch which feeds separate pair of BC oscillator coils, and once switched to SW position, feeds the 1 SW osc coil all located under chassis. Following JF Riders alignment procedures, I first injected accurate 175 KC to the grid-cap of the 2A7 and tuned/peaked the 2 separate IF trans to 175 kc for max output using lowest output possible from RF gen.
Then step 2:, re-adjust RF gen to accurate 1400 KC, then set radio dial scale to 1400 kc, inject the 1400kc thru ant wire via .00001 uuf condenser, & peaked up all screws on 3-gang tuning condenser for max volume.
Step 3:, set RF gen to accurate 700 kc, and "rock the tuning condenser" back and forth while adjusting the BC band chassis mount oscillator trimmer to set the appropriate position and match the freq to the printed plastic dial scale.
Step 4: go back and peak up all 3 screws on 3-gang tuning condenser for max.
Distant stations at night dont "double-track". Therefore, since I have the set aligned to specs, perhaps my 35' outdoor longwire ant is overloading the ant circuit? I have found on many of the TRF sets similar antics from nearby powerful AM broadcast stations showing up in more than one-place on the dial also.
I may just need to use a shorter pc of antenna wire for nearby stations, as these old 33 type model radios antenna connections can easily overload these days? Otherwise than hearing the nearby local powerful stations double-track (on strong local stations only),... otherwise, the set is working properly. The SW band recept is weak, but so is orig chassis design. I may be getting the best reception this set has to offer already? Thanks for any suggestions!!

[exray]

Texasrocker Wrote:Distant stations at night dont "double-track". Therefore, since I have the set aligned to specs, perhaps my 35' outdoor longwire ant is overloading the ant circuit? I have found on many of the TRF sets similar antics from nearby powerful AM broadcast stations showing up in more than one-place on the dial also.
I may just need to use a shorter pc of antenna wire for nearby stations, as these old 33 type model radios antenna connections can easily overload these days? Otherwise than hearing the nearby local powerful stations double-track (on strong local stations only),... otherwise, the set is working properly. The SW band recept is weak, but so is orig chassis design. I may be getting the best reception this set has to offer already? Thanks for any suggestions!!

If you dump an extremely strong sig from the sig gen into the front end do you see the double peak? I'm kinda torn trying to decide if the ant may be detuning the set somehow or if its plain old Miller Effect occurring with the strong signals?

I've never had a signal on a TRF show in more than one place. In a case like that I would suspect overloading creating mixing products. I've only got one strong local here...it doesn't have anything to mix with But in the case of the superhet in question, sure I'd expect to see images 350kc away from the fundamental.

I'm curious about your double peak ~5kc apart.

-ex

[exray]

Oh duh...I got to thinking about your bc padder trimmer not having effect. That may be the key. It could be very possible to have one of the two antenna/rf trimmers (C2 and C4) maxxed out at what appears to be a max but isn't because its at the end of range. And the other trimmer still in range.

Or both of them maxxed out and peaking at different freqs.

I guess the way to tell is to know out if either trimmer is fully tight or fully open?

Do you get the double peak at both ends of the band?

-ex

[etech]

Exray,

Check your pm.

Regards,

Ed

[Texasrocker]

Hello Exray, I didnt receive your PM.
I have temporarily moved the Am Bosch mod 350 aside on my workbench, and completing total restoration on a 49 GMC truck radio for a customer. Thank you for all your help in why it is double-tracking!!
I will be able to check into that issue again next week. I will use your suggestions of checking further into the BC & SW oscillator chassis mount trimmers. The prob must be there indeed!! Thanks again for helping me!!

[exray]

Texasrocker Wrote:Hello Exray, I didnt receive your PM.

Good reason for that. I didn't send you one .

'etech' was just finding me here, sorry

-ex

[Texasrocker]

...sorry for that confusion Exray! "My Bad"! I confused the replies on this post. Thanks again for all your help!! Im gettin to be a ol-fa*t , and have a hard time seeing small letters on my laptop sometimes.