Re #55 Marcs speaker:

Perfect!

A quick coat of stove black and it would look like a new one!

Fred.

You will be all sick of me shortly if not already , I could do with some advise before I wire to much up. I do not want to have to rip out wiring because I made a stuff up. My questions are these.Where should I be using shielded wiring eg wiring up the IF cans , the volume control and front end coils . Secondly what can I use, and where can I get some? I was thinking of coax but it is too heavy and bulky. There must be some very small coax that would be suitable. I also have another question regarding the two specified wire wound resistors there is a 375 ohm ww resistor specified on the cathode to ground of the 6V6 , I have used 390 ohm 1 watt carbon resistor. The other is a 150ohm on the cathode of the front end valve 6J8-G I Would think this is for stability,cannot see why it is particularly necessary for the 6V6. I am finding this project more challenging than repairing old radios and I feel a bit of a dummy these were built in the thousands by people with no, or very little electronic background and yet I find myself in areas of uncertainty. In regards to the shielded wire I guess I could buy some RG 58 coax with a tinned outer braid remove the outer and inner leaving the braid then run in some thinner wire and stretch the braid back over it , that should work . I guess the biggest question is where is it needed . I don't want to power it up and find it to be totally unstable oscillating and screeching I can oscillate quite well by myself.
If I have to use ww resistors in those two places they probably will have to be those ugly 5watt jobs with the square cement stuff around them there does not seem to be a lot of choice in ww type resistors.
Regards Jim

Both these resistors provide the bias for their valve and in each case, a 390 ohm and 150 ohm, 1 watt carbon or metal film resistor is fine.

I would think a shielded cable around the volume control leads would be necessary, but other areas should be fine if you pay attention to keeping leads as short as possible, close to chassis and keeping things neat.

Harold

On a Kriesler set I have seen leads to the volume control run through tinplate tubes soldered to the chassis. So if nothing else is available some sort of small tube would do.
Some earphone/earbud leads are coax, if you have any with cactus leads. This might do for audio going to and from the volume control.

Thanks Harold.

I made up some shielded cable from a piece of RG58 coax ,stripped off the outer sheath pulled out the centre piece ,inserted a piece of cloth covered single stranded push back wire then smoothed the braid out over it stretching it so it lies tightly over the inserted wire looks like the original stuff. I have used some between the the grid of the 6V6 and the wiper of the volume pot via the 0.01 cap should I shield the other sides of the pot to the IF transformer and the other side that connects to the cathodes of the mixer and first IF valve I guess that is the avc bit. The way I am going I will have the ability of a 12 year old again.
Kind Regards Jim

Thanks STC 830 also ,your post showed up after I replied to Harold.

Yeah, I have been caught that way too - I have to try to remember to bring the thread up to date before posting.

The Kriesler was I think the 11-5 (timber with twin tuning dials), I remember it particularly because it is the only radio I have seen with oil filled caps; though it might conceivably have been an 11-7.

Jim you are doing fine.

Yep use the 1 watt resistors if the one on the 6V6 is too small in case size it will just get hot.
You can then stick in a WW.
Re the shielded wire, you can always just wire up with plain wire and see how the hum level is.
Then you can go for the shielded bit by bit to fix.. Your RG58 mod cable sounds great.

I have made guitar amps and radios without shielded wire it all depends on whether sensitive grid runs are close to anything with 50Hz leakage. Then a length of shield fixes the hum level.

Like I said you are doing fine and finding how different it is starting from scratch rather than with something where all the questions were answered by someone else. There is so much taken for granted, until you start with a bare chassis!

Forwards mate!

Fred.

Thanks Fred onward and upward I hope.
Regards Jim

It is rare to find 50K & 500K resistors in spec on Output tubes, they just chew them up. You can get 2 & 3 Watt resistors that look like ordinary ones. Have not bought any for a long while pretty sure it was EVATCO & its changed hands since then. They may have other bits you want.

The grid resistor is not the 6F6 tube bias if there is a cathode resistor. Beware of the plate resistor on the first audio they to have an attrition rate. The voltage drop across the cathode resistor can be most informative.

Rust is of concern if it happened after you got it. AORSM circuit is a horror. Agree 1watt on 6F6 cathode; what looks like R24 appears to be "Back bias" 20 Ohms that will tell you current draw. Check it & if its cooked that's an overload & do not heavy it up, find the source. if it has 450V filter caps with a 5Y3 that's the first place to look. Then heater cathode shorts weird until you see it happen. High resistor will have more volts across it than it should. That is shown with a shielded transformer: Those get an earthed cable here. They put a charge on the chassis.

Marc

Hi Marcc this relates to the AWA 191 not little general ,not to worry I appreciate your input . I replaced the grid bias resistor that doubled in value. It is usable now but in the future I will have to dig deeper it is still a bit down on volume . You are right about the AROSM circuit it is very difficult to read. One of the reasons I did not dig deeper at the time the other is the nuts holding the speaker look like they have rusted up. Did not try to undo them . No reason they should have as it is in the Hallway not exposed to the elements . This. Is a very difficult radio to work on as you mentioned the circuit is close to unreadable and secondly the push button tuning occupies the centre section of the chassis and has to be removed to acces a lot of the components . However the 6F6 is accessible. The speaker if I remove it is also huge and takes up a lot of bench space I don't have. Actually my bench space it the end of the dinning room table.
Happily my wife Robin is not complaining , after all the dinning room table looks quite different to what is on most people's dinning room table.
Regards Jim

Now seeing my last attempt got caught up in a tangle, which Brad has sorted. That electrical comment was based on the 191 in AORSM's. Rust is of concern if the building cannot vent moisture.

It is amazing with modern buildings how much they can build up if not vented & most new houses are a cocoon. One only has to turn the Bathroom fan on and then open a door or window to appreciate the vacuum created. At the moment I can leave the door with the security screen open allowing the bathroom to dry out & the house to breath a bit. If I am home I can open the house to any of the four winds to air it.

Many forget condensation: That's why shed 2 is fully insulated along with the roof of shed 1. That stops condensate forming on the roof of 1 and the roof & walls of 2 on the inside. The house roof is also vented for the same reason plus the geese vented the bathroom & for a short time the range hood into the roof cavity. That was in the contract not to happen.

The workshop at the moment is at 52% RH.

Even that I am single computers & Radio's for repair are banned from the house. Its a house: Not a workshop. Radio repairs & quite a few others are confined to shed 3 which was an Art studio 30 by 14 feet. Engineering & Turning & Fitting, engine repairs and that sort of caper are done in the 100+ year old shed 1, also similar size, but with a skillion which is the car corral. This can be interesting, and exercise, as various bits & pieces wander back & forth between sheds 1 & 3 which are around 60m apart.

Marc

Hey Jim, the dining room table was what I made my first guitar amps on.
It was the only table we had!

I used to bend the chassis front and back faces in the back door jamb.
All I had for tools was scope soldering iron and a black and decker 3/8 drill.

Got a bit crowded with my stuff down one end and Barbara's sowing machine and art stuff up the other!

That explains why I wound up with a large workshop out the back.
No space in the dining room for the lathe and drill press etc!

Its not where you do it that counts, its what you do.

Fred.

Hello Marcc and Fred.
It all comes down to space, Marc sounds like you have a great place down there ,we live in a gated security estate with a modern house and small two car garage, used to be able to do some stuff in the garage , still do, however I sold my little 1969 Hillman Hunter and replaced it with an 2007 extrail and that being 1/2 meter or so longer meant my workbench had to go . The benifits of living here out way the disadvantages able to walk the dog down to Lake Illawarra foreshore (KANAHOOKA point ) and Coonawarra bay without getting into a car and driving there, also 12 minutes from two major hospitals plus countless medical services which unfortunately these days are being utilised more often than what we would like. Some years ago looked at a property down Batemans Bay , great house plenty of workshop space but reality set in as you get older we need to have good hospitals close by so the idea was canned . So the dinning room table was looking very attractive, I can't just sit and do nothing have tried but it does not work. Fred what a great idea sheet metal bending in the door frame,probably have to wait till Robin was out before I try that.
Still progressing with the Little General trying to sort out the wave change switch one of the coils looks a bit sus. If I have too much trouble I will find a suitable aerial and osc coil and leave it as BC only . I will never use the SW band anyway, just trying to make it as per the article it is starting to look a bit more like a radio . Who knows in a day or two may get to power it up.
Regards Jim.