Hi guys,

So I've just recapped the above stereo gram & quite happy with it - sounds way better than you'd expect! And with a new Sonotone 9TA cartridge the vinyls are great too!

One little issue I have though is that the right channel is a lot less 'bassy' than the left channel in all modes.

Additionally the right channel sometimes drops out on playing vinyls although never drops out on radio.

Both have me quite puzzled....I've swapped the 6gw8's around from R to L channel and no difference and wiring all looks in good order.

Is there any easy way to try & diagnose this? I'm quite the amateur but would you recommend checking the voltages of the tubes next - the Kevin Chant site has the 11-97 schematic and various tubes have voltages showing - is someone able to tell me how to identify the relevant pins from under the chassis? https://www.kevinchant.com/uploads/7/1/0/8/7108231/11-97.pdf

Or is a less bassy channel a sign that an output transformer is weak? or speaker? I guess I can cut & resolder the wiring to the speakers to try that...

With the right channel dropping out on records - since most of the same circuit is used for both that and radio - I assume the issue must be with the pickup. The wiring in the headshell seems alright but I will have to remove the turntable to inspect the mute switch - are the turntable muting switches prone to failure? There seems to be a capacitor and resistor on the muting switch too.

Any help much appreciated guys!! Thanks

It is one thing to change out the caps and another to check all of the resistances for another. Often it takes an audio generator, or just a signal generator to catch out what is causing a signal issue, in conjunction with an oscilloscope. It is also possible to have put in a wrong value part.

As its Stereo: Measure all of the voltages; These are on the schematic https://www.kevinchant.com/uploads/7/1/0/8/7108231/11-97.pdf

Dropping in and out only on Pick up is likely a switching or mechanical, fault like lose wires, bad solder jointing, dirty tube pins, and bad plug & & socket connections. Do check the tone control caps to make sure they are a pair.

Marc

Thanks Marc I think you helped me years ago on my last 11-97 too! That's interstate at my parents place now....so figured I'll just buy another one & recap it.

One thing though - how do I work out what pins I'm measuring the voltage at?

Looking under the chassis seems like it will be tricky to ascertain pin numbers?

I haven't checked the resistors but that will have to be next on the list....with the channel dropping in and out I've just had (another) tinker and sometimes I seem to be able to get it working again by pressing the off button and then pressing the gram button again....so perhaps something is going on within that switch so the chassis will have to come out again to investigate that....although doesn't seem like that has anything to do with the lower / less bassy sound from the right channel as that is a constant on gram and radio....

Fun & games!

Looking under the chassis seems like it will be tricky to ascertain pin numbers?

Pin numbering diagram here. Note viewed from under the chassis.

https://electriciantraining.tpub.com/14178/css/The-Envelope-24.htm

Oh that’s great thanks. One important question though - I have spare tubes here from an 11-95 and figured I’d swap a few just on the off chance one may work better. Well I swapped the rectifier tube & the transformer started bubbling! Omg I couldn’t work out what was going on….it’s the same 6ca4 tube….can’t work it out but sounded like a waterfall under the lid.

So anyway I’m now nervous about it….I put original tube back and it all works ok still so I must have just got it off just in time….but is it going to be safe to use now?

Can’t believe that happened ahhhh are replacements even available?! Probably not…

Edit: transformer runs hot now so probably ruined. Ahh anyone have any Kriesler transformers? Or have a substitute I can source? How depressing!

In amongst the pile of scrapped radio's acquired for parts scavaging and the odd radiogram, I believe there is a 11-97 with the chassis out of it.
Interesting winter project resurrect the chassis & burn the cabinet to keep warm doing it.

It sounds a bit Like the Peter Pans that came in for chassis repair one is stamped FKM & is a factory modified chassis and is actually a FNQ.
GKL is full of rotten wire, but for the first time since an Astor JJ, decades ago, the earthy side 60K resistor of the 45V voltage divider is open as is the 30K which id burnt & open. All on the 6A8. That tube and the rest will see the tube testers before putting back & I doubt 6A8 will be going back as its probably shorted?

If it looks like the tube is shorted do not sub it into another set, I have seen a few 6 & 12BA6's shorted lately.

When starting up I always have an analogue meter on "B" and if voltage is not going as planned one hits the "Kill switch". With a heater tube It does pay to use an ohmmeter heater to cathode as that will often pick up a heater to cathode "dead short". They can be very destructive and render the device a none commercial / not cost effective repair.

Unfortunate: Keep an eye out for a tube tester, seem to be a lot of deceased estates of late. I went to a funeral last week & could go to another this week, perhaps a second, albeit that one may be next week. Averaging two a month since November.

So many people dying to get out of the place, never seen so many locally.

If you look up the data sheets they show pin outs: Normally convention with Octals & Miniatures, is clockwise looking at base or wiring side. From the gap in the pins: Miniatures and the spigot: Octals

Thanks for all the help - yeah the damn tube has ruined it I think. Oh do you have a parts 11-97 or just the cabinet? If you have a parts chassis can I buy it? I can only find 1 other & it’s a 4 hour drive away.

No good about funerals sorry to hear about that…. Hopefully just a coincidence & there’s no more….

I am just outside Wangaratta & that's a long drive depending where you are? I keep out of the place.

The whole thing is in a container with a couple of other radio grams That need to be gotten rid of.

I will retrieve the chassis & see if the tranny looks ok later. Its wet here, so its continue fixing & adding wire & powdered rubber to the floor I just swept.

I’m in Brissie but I’m always down Melbourne as my family is there - actually have a mate driving up from Melbourne later in the week too I think Wangaratta could be on the way I can check!

If you don’t mind having a look that would be FABULOUS as I am so upset a silly old rectifier tube has done this! Won’t make that mistake again….

Hope the rain stops for you soon!

I need the rain to grow grass. Unusual Autumn many of the grapes, fruit trees & roses etc. have only just started to drop leaves.

I may actually get one of the mowers out as the lawn is growing faster than the feral sheep can eat it.

Will let you know what I find.

Marc

Ok mate that would be greatly appreciated.

I think my neighbours are probably enjoying the quiet after the last week of constant vinyls haha

Cheers.

If you don't like the vinyls they do dissolve in some solvent's like metho, or acetone so you can turn them into some thing useful.

Its an each way bet the chassis here is an 11-133 from 1971 no listing on the transformer Its 18- something and this one is not the "B" model. This runs 6M5's with a similar tube line up and looks like 100mA draw on "B" with less voltage. However the chassis is only missing a 6M5, which is solvable. It will not need caps, they're Polyester.

Interesting they went back to 6M5. I replaced the transformer in a Thorn running 6GW8 which was promoted as an audio tube. One shorted & caused a chain reaction.

You can have this chassis

https://www.kevinchant.com/uploads/7/1/0/8/7108231/11-133b.pdf

Marc

Really appreciate the effort you’ve gone to its most kind.
I think that chassis is too different to fit in my 11-97 cabinet but do you think that transformer would work n my 11-97 chassis? Mines an 18-4150 (whatever that means!).

Not all transformers are the same and whilst the same one may appear in several models, the current draw, voltages and physical size also play a part. The other parameter often not realised is the duty cycle. Transformers are not supposed to exceed a certain temperature, so those running 24/7 will be larger.

In this case we compare transformers, to get their part number. You will often within the same manufacturer, find the same part number in other sets. I don't have data on the 11-133 transformer, but its a valve rectifier. The "B" model uses a full wave rectifier, therefore will have no centre tap.

We do know what the HV winding voltage is and current draw of the 11-97. I would suspect that this transformer may work, even that its less voltage. Less voltage would draw less current.

Marc

Hi Marc sorry I’ve been out most the day. How soon do you need to get rid of the radios? I’d like to try & find a proper replacement but I don’t know what my chances are of sourcing another 11-97….and if I can’t I’ll try & get your chassis & mod that to suit.
Wish I bought a few of these years ago when they were being thrown to the tip!