Sherwood S-8910 Tuning meter adjustment

[Eastham]

Hi, guy's. Hope I'm posting this in the right sub forum, as it is a receiver but I figure I should come here for help with the tuner bit..

So here's my Issue, the Tuning meter seems to be out of alignment when off station, this was taken at the furthest end of the scale.



The signal meter deflects to nil if I disconnect my ghetto antenna... But the tuning is always off center like that, I was looking around and found a adjustment for the signal meter and one for the tuning meter. My question is this normal for the tuning meter and if not can I adjust the tuning meter without all the special doodads that are required for most tuner ajustment, thought I'd ask here before I went and tried to cener the tuning meter with the pot and probably screw something up, I learned not to mess with tuner stuff without the proper equipment the hard way...

Thanks.

 

[I LIKE MUSIC]

Per the service manual. If the center tuning meter is centered when the receiver is turned off.



T201 is the first adjustment.

This can be done with the receiver tuned off station with the FM antenna input terminal shorted to prevent unwanted signals/electrical noise from pulling the center tuning meter off side. Adjust T201 for zero voltage as noted in the service manual.

Then if needed adjust VR203 to center the center tuning meter.

This should get your very close.

Be sure to use the correct alignment tool for T201 (non metallic, correct size).

 

[Eastham]

Per the service manual. If the center tuning meter is centered when the receiver is turned off.

View attachment 1002565

T201 is the first adjustment.

This can be done with the receiver tuned off station with the FM antenna input terminal shorted to prevent unwanted signals/electrical noise from pulling the center tuning meter off side. Adjust T201 for zero voltage as noted in the service manual.

Then if needed adjust VR203 to center the center tuning meter.

This should get your very close.

Be sure to use the correct alignment tool for T201 (non metallic, correct size).

Thanks for the quick reply, when the tuner is off it falls to the middle, it's just when it's off station that it is off center but when I tune the tuner into a station perfect signal is at center of the meter, would centering the meter effect this?

 

[Eastham]

Per the service manual. If the center tuning meter is centered when the receiver is turned off.

View attachment 1002565

T201 is the first adjustment.

This can be done with the receiver tuned off station with the FM antenna input terminal shorted to prevent unwanted signals/electrical noise from pulling the center tuning meter off side. Adjust T201 for zero voltage as noted in the service manual.

Then if needed adjust VR203 to center the center tuning meter.

This should get your very close.

Be sure to use the correct alignment tool for T201 (non metallic, correct size).

Just did the adjustment's and thank you so much! I swear the tuner is picking up more stations in FM only then it ever did! and the centered Tuning meter pleases me. If you don't mind explaining, what did making those adjustments do? I know T201 was way outta whack, 300mV!

 

[I LIKE MUSIC]

In simple terms, T201 controls the circuit that converts the radio signal (RF/IF) that we can not directly hear to an audio signal that we can hear.

VR203 just calibrates the center tuning meter to read correctly when T201 is adjusted correctly.

 

[Eastham]

In simple terms, T201 controls the circuit that converts the radio signal (RF/IF) that we can not directly hear to an audio signal that we can hear.

VR203 just calibrates the center tuning meter to read correctly when T201 is adjusted correctly.

Ah, that's pretty neat. Suck's that my country is going to be killing FM in the coming years in favour of DAB like Norway.

 

[I LIKE MUSIC]

I am glad that you got it working.

Too bad a about the transition.

 

[Eastham]

I am glad that you got it sorted.

Thanks again, for the help!

 

[smead]

Resurrecting this old thread. I'm having the same issue as the OP, but am not sure I have the needed alignment tools / expertise to perform the steps outlined above from the service manual.

When my 7910 is off, tuning meter is centered. When on, the FM works, but is very weak in that I can't get more than 1-2 of signal strength on local stations when other receivers with same antenna get 5. And when it does weakly tune in the strongest station, the tuning meter is off center.

I have a dvm, and follow step A in the above service manual steps, but in step B I'm not sure what is meant by " tune the core of the transformer T201".., and not clear what non-metallic tool is used to do this.

I can use the dvm to test things, but have never worked with a tuner. I'd really like to fix this so I can fully enjoy this great sounding old receiver, but don't want to go from bad to worse by messing it up.

Advice would be appreciated - thank you!

 

[8-Tracked]

Ah, that's pretty neat. Suck's that my country is going to be killing FM in the coming years in favour of DAB like Norway.

Will be taken over by local analog broadcast in most countries.
But UK go digital radio broadcast only? t's not going to happen after all I think. Lot's of countries have reactivated there analog ON-AIR broadcast infrastructure by resurected or build new 'masts', towers, antenna's, switches, repeaters or repaired them, you see.
And all of that after 'they' first went with a lot of 'kabal' from analog to digital 'only' broadcast). And there are very good objective reasons for this 'reactivating' analog on air broadcast infrastructure!

 

[smead]

Good to know about FM in the UK, but can anyone help me adjust my 7910 tuning meter?

 

[bobschneider]

Good to know about FM in the UK, but can anyone help me adjust my 7910 tuning meter?

There’s a slug in the middle of top of the T201 transformer which you turn to adjust it. The tool for doing so is a plastic hex key. These slugs are very fragile, so if you use a metal tool, or try to force it, you can break it. The tools are along the lines of the following

https://www.amazon.com/Philmore-Universal-Color-Alignment-Trimmer/dp/B019ZT5OOS/ref=sr_1_2?crid=12T1A9NA6UA0W&keywords=tuner+alignment+tools&qid=1652322396&sprefix=Tuner+alignment+tool,aps,75&sr=8-2

 

[smead]

Thank you so much for that, I'll order and give it a go. I unfortunately could not locate the R220 resistor per step A. I see a pole labeled "TP" on the upper right corner of the board, but no R220. Any help locating this and specifics on how to connect the DVM would be appreciated. Sorry for the dumb questions, I'm new at this. Other than the bad FM, this old Sherwood sounds sublime, rocked Rush and the Doors in the garage all afternoon. Amazing punch and clarity for 60WPC.

 

[R-2-R]

https://www.hifiengine.com/manual_library/sherwood/s-7910.shtml.

Thank you so much for that, I'll order and give it a go. I unfortunately could not locate the R220 resistor per step A. I see a pole labeled "TP" on the upper right corner of the board, but no R220. Any help locating this and specifics on how to connect the DVM would be appreciated. Sorry for the dumb questions, I'm new at this. Other than the bad FM, this old Sherwood sounds sublime, rocked Rush and the Doors in the garage all afternoon. Amazing punch and clarity for 60WPC.

 

[amptramp]

Sherwood has been known to make undocumented changes during a production run. Your schematic may not reflect the as-built configuration.

 

[R-2-R]

Sherwood has been known to make undocumented changes during a production run. Your schematic may not reflect the as-built configuration.

Just about "every manufacturer" has done that or does that.....nothing new.

Most of the time, if you read the fine print, they will state that they may have changes from when the first print on their manuals, schematic's, etc. for their equipment regarding parts, layouts, etc.

That is why one needs to find out if there are, or have been any "Revisions" and or "Updates"...etc. on any specific manual, schematic's, etc.

 

[Ylli]

When on, the FM works, but is very weak in that I can't get more than 1-2 of signal strength on local stations when other receivers with same antenna get 5

This is not something centering the detector will fix.