Sherwood tuner died.

Wasn't he a famous playwright?

You aren't getting confused with Robin Hoods 'hood' are you?

T i m

Are you sure it's the tuner and not the amp to which it's connected?

T i m wrote:

Take it you don't have a schematic so that would be your first step. Then trace with a signal tracer and see if you can find your missing audio?

Hi!

Well, I think that the first thing I'd do is check the controls on the amplifier. Make sure that nobody's turned on a "tape monitor" switch or something along those lines.

And if that fails, have you tried the tuner with another amplifier? Changed the cables going from tuner to amplifier? (I mention this because I had a set of RCA audio cables recently that didn't work but did not test open anywhere. For whatever reason, the shield connection was very high resistance.)

If you want to test the AM side of things, your finger or a short piece of wire will do in a pinch for an antenna.

William

Yes because it's a receiver (tuner amp) and all the other inputs seem to be ok (I was listening to some streaming audio via my PC earlier via the AUX input).

The thing is, I thought it was the aerial as it feeds two radios we have here and neither work. However, putting a bit of wire in the back of this Sherwood gave exactly the same effect (we have a strong FM signal round here).

Cheers, T i m

Checked.

Sorry, it's a tuner - amp (The AUX was working earlier and I'm using the CD in right now).

Ok, I'll give that a go, thanks.

Cheers, T i m

No and it would yes. ;-(

Yup ... or hope it's a common fault and someone tells me to cut D54 out and put up with the inter-tuning noise. ;-)

Cheers, T i m

I think this is the service manual for what could be the same model inside (the controls seem to be in different places but the same range of controls).

Could it be Q8R/L, top right on their P8? They seem to specifically mute the output of the tuner but if both channels are quiet, what are the chances of both devices being faulty? Does this then leave the tuner itself or maybe the control inputs(s) to the tuner mutes?

I guess the mute it refers to here is how it kills all the unwanted outputs being mixed together (rather than the master 'mute' on the main amp as such)?

I've not read all the manual yet so maybe the answer is there so I'll carry on RTFM. ;-)

Cheers, T i m

If memory serves, didn't those units have AUX IN and OUT in the back where you had to place jumper cables in ? other wise, you didn't get any sound.. Maybe a little leakage but that was it.. ALso, maybe you're using an EQ that isn't working?

Erm, I think it has a tape loop but that's about it? I'm pretty sure it *was* working ok and now it isn't and I've not touched it round the back for *years*.

Nope, this is an all_in_one receiver. I've since found the owners handbook on the net:

I read the service manual through yesterday and I think I have a slightly better understanding of how the mute thing works for each of the in / output and now don't think that's the problem. I turned the volume right up when it was on FM and could tune it in to many stations [1] (that you could just hear in the background). Then when you selected say the 'Phono' input the set went quiet (suggesting the FM was being 'muted' when de-selected and therefore (probably) un-muted when selected).

The faultfinding suggests a transistor or a couple of ICs just after front end could be at fault so I might go in there for a look sometime.

Alternatively I could look for a compact DAB tuner and plug that into the AUX as that seems to be the way we are going these days (even here in the UK).

Cheers, T i m

Ooops, bad form (again) I know ..

Cheers, T i m

Digital tuners often exhibit a problem where the discriminator alignment drifts enough that problems similar to yours occur.

Really needs to go to a shop. It's a simple alignment, but not for a DIY with no service manual or training.

Mark Z.

The indicator light might be burned out. Or, as someone else is pointed out, the tuner might be slightly out of alignment.

Ah, ok.

I think I now have the service manual so potentially some test / alignment procedures to follow. I have a scope, DMMs and frequency counter etc but no signal injection kit but could probably rig something if need be.

I would be happy to take such a thing to 'a shop' 1) I don't think we have many over here (UK) any more and 2) if we did I think the work would probably out-value the equipment?

I have been an electronics service engineer for much of my life it was mainly on data-transmission / communications kit. I even got my Radio Amateur ticked to do Packet radio. ;-)

I've had a look about and a DAB / FM tuner can be had for about £60 new so I could use that instead of the tuner part (I'm not too bothered about 'quality' as long as it sounds ok and works).

Cheers, T i m (G7ICW)

p.s. I might see if I can find a local 'radio enthusiast' who might be interested in having a look for a beer.

Could be, and certaily a good starting point. Maybe open the collector and see if you have audio (there). Also check the input to the low pass filter that feeds the audio. If there is no audio on the optput of IC3, you may be SOL...

It's part of the fluorescent display so difficult to tell.

Whilst I'm sure that's not impossible I'm not sure how likely? I say that because I've had many radios / tuners / scanners over the years and I'm not aware of that happening, especially without some external influence. However, I guess components can age, capacitors dry-up etc ...

I will have a quick look in there and see if the schematics I have look correct for my unit and then see if I can follow anything through and some of the alignment procedures that I can with my limited (for this sort of work) service equipment. I guess even a tweak of a pre-marked coil or pot should tell me if I'm in the right area or not (no difference = wrong area or it's *way* off / broken)). ;-)

As I have mentioned elsewhere, a safer, quicker and potentially better solution (as no one has come up with a specific weakness / experience with this particular unit so far) is an external FM / DAB tuner as then I can enjoy the DAB stuff as well.

Cheers, T i m

Extremely common.

Mark Z.

Typically there are two test points physically near the discriminator transformer. One uses a DVM to measure the DC millivolts across these two points, while tuned to a station near 98 mHz. Adjust for zero millivolts. A center bar-graph display, such as seen on Fluke meters, is useful - one can adjust the moving voltage to center around zero.

Mark A.