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Old 2nd Jan 2019, 9:47 pm   #1
Humptydumpty
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Default Trio 9R-59D receiver problems.

Would anyone know the name for the wire that goes from the PCB up to to the AF potentiometer. The wire is black, it's shielded and single copper PVC coated inside. I need to replace both wires from the pot to the PCB to make a nice job of it.

eBay is no help. Well may be it's because I don't know what I am looking for. Can anyone help please?
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Old 2nd Jan 2019, 10:21 pm   #2
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Default Re: TRIO R9-59D Potentiometer wiring

Hello Trevor.

Do you mean the name for the type of wire (shielded) used?
The answer to that is coax, or coaxial cable to give its proper name.
If I've failed to understand your question, I apologise.
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Old 3rd Jan 2019, 1:55 pm   #3
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Default Re: TRIO R9-59D Potentiometer wiring

In the UK it is screened wire. Elsewhere it is shielded wire. It may be lapped screen (thin screening wires simply wrapped in parallel spirals around the core) or full coax (some sort of woven screen). Lapped screened wire is OK for short audio connections; it may be cheaper than coax, and will usually be more flexible.
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Old 3rd Jan 2019, 7:07 pm   #4
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Default Re: TRIO R9-59D Potentiometer wiring

Quote:
Originally Posted by g4aaw pete View Post
Do you mean the name for the type of wire (shielded) used?
The answer to that is coax, or coaxial cable to give its proper name.
If I've failed to understand your question, I apologise.
g4aaw pete, Thank you but i have put all names in to ebay and other radio wire makers and i find nothing like i need. It is not solid copper but all i can find is multi strand centre. I was told by a good member of the forum that its audio coax. But find it i can not. Phil G4SPZ said he would let me have a metre from him so its sorted for now. Thank you.

G8HQP Dave, thank you for your help.
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Old 3rd Jan 2019, 7:35 pm   #5
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Default Re: TRIO R9-59D Potentiometer wiring

I'd have just ysed something like the ubiquitous UR95-type 'mini coax'.
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Old 3rd Jan 2019, 11:11 pm   #6
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Default Re: TRIO R9-59D Potentiometer wiring

HD

Type "screened audio cable" into Google

Also "Microphone cable"

Fred
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Old 4th Jan 2019, 11:17 am   #7
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Default Re: TRIO 9R-59D Potentiometer wiring

Unless you're dead set on originality, solid or stranded inner won't make any difference at audio frequencies.

For solid inner, you would be better looking at miniature RF coax than audio or microphone screened cables- by their very nature these need to be flexible and so will be stranded. At UHF frequencies in miniature coax, solid inner provides more closely controlled dimensions to provide better constancy of the characteristic impedance.
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Old 4th Jan 2019, 1:08 pm   #8
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Default Re: TRIO 9R-59D Potentiometer wiring

Sadly, because of the foolishness of some audiophiles, ordinary cheap lapped screen cable has almost disappeared from catalogues. Even when present, it may be 'OFC' - quite unnecessary, but more expensive.

You may be able to buy a twin version and separate the two.
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Old 5th Jan 2019, 5:08 pm   #9
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Default Re: TRIO 9R-59D Potentiometer wiring

Thank you all for the information given to me.
With the help of another good member of the forum - Phil G4SPZ and his donation of a metre of the audio cable. I was about to pay him for this but no way would he let me do so. Thank you Phil. I have been a bit of a pest with emails by the dozen to Phil. Dont know a much about electronics. If it is a mechanical fault i can fix it, like if i can see a broken wire or a valve not lit up i can sort it. I am only a SWL and a lot of old radios went through my ownership. I used to pick them up you know the old valve sets 4 for a £ in B.ham back in the 1960 era. Some made it some never even lit up. Thank you again.
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Old 11th Jan 2019, 2:03 pm   #10
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Default Re: Trio 9R-59D receiver problems.

I’ve been communicating with Trevor via PMs, which are a bit unwieldy.

So far, he has successfully replaced the volume control and the receiver is working, but with constant hum. He has established that the HT at the anode of the output valve (pin 5) is only about 40 volts instead of the normal 200 volts. I have now asked Trevor to measure the valve’s cathode voltage to see whether the low HT is being caused by excessive current draw through the output valve or simply by a faulty reservoir capacitor.

Trev, can you now please let us know what make and model of multimeter you are using?
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Last edited by Phil G4SPZ; 11th Jan 2019 at 2:05 pm. Reason: Update
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Old 11th Jan 2019, 2:25 pm   #11
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Default Re: Trio 9R-59D receiver problems.

HD.

If you can clarify which model you have I'll post up a circuit extract.
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Old 11th Jan 2019, 2:40 pm   #12
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Default Re: Trio 9R-59D receiver problems.

Quote:
Originally Posted by Phil G4SPZ View Post
So far, he has successfully replaced the volume control and the receiver is working, but with constant hum. He has established that the HT at the anode of the output valve (pin 5) is only about 40 volts instead of the normal 200 volts. I have now asked Trevor to measure the valve’s cathode voltage to see whether the low HT is being caused by excessive current draw through the output valve or simply by a faulty reservoir capacitor.
Remove the output valve, measure the anode volts, if then ok try another valve, lots of these available.
On the subject of hum ( unrelated to low HT) please check for dc volts on the input grid of the valve, if any found replace the capacitor on the grid, does not need to be exact value, it allows the AF to get to the valve and isolates the grid from DC.
you will fix this radio as very simple circuit and also these preform very good

MM0HDW
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Old 11th Jan 2019, 5:36 pm   #13
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Default Re: Trio 9R-59D receiver problems.

If the set in question is indeed a 9R59DE/DS with two circular dials, the Radio Constructor magazine in Oct 1970, and in March and April 1971 carried a series of modifications by Martin Lindars in Radio Constructor, which included modifications to reduce hum. I'm not suggesting that those modifications will cure an abnormally high level of hum in this particular set, but it certainly reduced the hum when I did the mods on my set. Namely, to reposition the output transformer beneath the chassis away from the mains transformer, and to fit a small LF choke across the reservoir/smoothing caps.

As the set doesn't have an internal speaker, the hum is especially noticeable when using headphones.

Here’s a clip from the articles:

Quote:

"The two basic shortcomings of the receiver are (a) excessive 50Hz a.c. mains hum - particularly noticeable when using 8Q headphones - and (b) oscillator instability above 15MHz. The first of these will disappear once the following modification has been carried out. The second shortcoming will be dealt with next month. The first cure for excessive hum tried out was to fit an additional smoothing circuit in the main h.t. line but this proved to be ineffective, only a small improvement being gained at the expense of a reduced supply voltage. The a.c. mains 50Hz hum was found to be almost entirely due to the siting of the output transformer on the chassis deck right alongside the mains trans- former. Upon re-siting the output transformer under the chassis the hum virtually vanished, proving that most of it had been induced between the two adjacent transformers”.

End quote.

He also stated that when he substituted the 6AQ5 output valve for an EL95 (no mods to the valve-holder wiring) that helped eliminate hum and distortion. (Mention was also made of re-siting some RF wiring away from the heater wiring). There were many other mods of which I carried out most, such as fitting a voltage stabiliser and crystal marker, for which provision was already made on the chassis, and was covered by a circuit in the user handbook.

Here are the links to the articles:

October '70:

https://www.americanradiohistory.com...RC-1970-10.pdf

March '71:
https://www.americanradiohistory.com...RC-1971-03.pdf

April '71:

https://www.americanradiohistory.com...RC-1971-04.pdf

Hope that's of interest and help.
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Old 11th Jan 2019, 6:39 pm   #14
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Default Re: Trio 9R-59D receiver problems.

I remember reading those Radio Constructor articles when they were first published, but I never modified my own receiver which I still have.

Before we start offering the OP too much advice, which may go over his head, I think we should establish which receiver he has and why he has such a low anode voltage on the output valve anode.
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Old 11th Jan 2019, 8:05 pm   #15
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Default Re: Trio 9R-59D receiver problems.

Hi and thank you for your help . I am out of my depth on the forum talking about electronics . Now if it was mercedes car engines i can talk about those
Well the help from Phil was a very big help to me .But i think i over did the pm side .
So the receiver is a Trio 9R 59D i have the owners manual and also a service manual .Nothing fantastic but basic diagrams and information .I will check out each post above and try and go through it the best i can ,.I only came on the forum to ask about a repair shop that could look in to it for me. I have a FRG7 thats deaf going by the performance that this old Trio .I would love to get it up to perfection. Thank you all again for your help .
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Old 11th Jan 2019, 8:23 pm   #16
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Default Re: Trio 9R-59D receiver problems.

Quote:
Originally Posted by David G4EBT View Post
...Hope that's of interest and help.
David i like the bit about the transformer ,that i could do i think i will need to look at it again . The 6AQ5 i have changed that along with the 6BA6.Waiting for two more valves to come it wont hurt to swap them out .Dont know how long they have been in there . I see V7 is used in 2 parts 7a and 7b i read that this valve could be a problem with hum so i have ordered one of those [6AQ8 and also 6BE6 ] .Funny thing about V8 shows less than 1 volt from pin5..
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Old 11th Jan 2019, 8:25 pm   #17
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Default Re: Trio 9R-59D receiver problems.

I didn't think there was a model 9R-59D, but I'm always willing to learn. Does it have twin round tuning scales?
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Old 11th Jan 2019, 8:34 pm   #18
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Default Re: Trio 9R-59D receiver problems.

My memory of the era was that the linear dial version was rarely seen in the UK with a Trio badge, I think most were advertised by the likes of Laskeys and GW Smith under the Lafayette banner. The amateur radio outlets sold the Trio 9R-59DS with its round dials behind windows.

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Old 11th Jan 2019, 9:11 pm   #19
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Default Re: Trio 9R-59D receiver problems.

This set was originally described in the thread title as an R9-59D which was clearly wrong, so it was edited to read 9R-59D.

There are several threads in the forums relating to 9R-59D. Some of these are clearly DE or DS suffix models. I'd love to know whether there was a model with a plain D suffix.
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Old 11th Jan 2019, 9:14 pm   #20
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Default Re: Trio 9R-59D receiver problems.

The difference...apparently:

http://televideo.ws/9r-59d.html

Lawrence.
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