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Old 21st Dec 2018, 2:55 pm   #1
TonyDuell
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Default Trio 9R-59 Shortwave Receiver

This is my first real restoration of a radio. I've done repairs, I've restored other electronic devices, but never done a full restoration on a radio set. So me being me, I picked something fairly complicated. A Trio 9R-59 shortwave set. I don't think this set justifies the name 'Communications Receiver'.

I bought it at a sale at the Dulwich museum. It was described as 'works, but has been got at'. When I got it home I removed the top and bottom covers and had a look. Most of the passive components had been replaced but the soldering was terrible. And I didn't like :

No mains fuse (holder missing, effectively shorted out)

Mains wiring joined with uninsulated solder joints in mid-air

Two core mains lead fed through a strain-relief bush and then knotted.

Bare component leads connected to HT+ crossing over bare wires connected to the chassis. HT insulation should not be by luck.

So I wasn't going to power it up in that state. It needed a rebuild.

The first hint for anyone working on one of these sets is that it was sold in the States as the 'Lafayette HE-30'. The manual for that set is rather more detailed than the Trio one, it includes parts lists and alignment data. So in general I worked from that.

With the covers off, I could make a start. Fortunately I noticed that the dial glass just slides in place. I removed it and stored it before it fell out. Then pulled all the valves and kept them in order just in case the inter-electrode capacitances were different enough between identically-numbered valves to upset things. The chassis will not rest on the bench upside-down, it stands on the adjusters of the IF transformers. But I made some 'legs' from Meccano angle girders fixed to the top cover mouting holes. So I could work on the set in comfort

A large part of the under-chassis area is occupied by the coil pack. After desoldering a dozen wires it was disconnected. Next I disconnected the BFO/Q-multiplier sub-chassis. Unscrewed the 4 screws for that and took it out. Removed the band switch knob and bushing (DO NOT forget to slide the nut, washer and earthing clip over the spindle when refitting the coil pack), undid the 6 screws for the coil pack (one hidden by the BFO unit which is why I removed that first), moved the coil pack to the side, unsoldered the earthing braids and took it out.

Then I started with the mains transformer connections, removing cut off ends of wires and rewiring things neatly. I added a fuseholder from the junk box which I connected in the neutral mains wire (!). The circuit diagram shows the mains switch in one wire and the fuse in the other so I kept it like that. I did fit a new 3-core mains lead with the earth wire going to a solder tag under one of the transformer mounting nuts. Yes I know it should be a dedicated bolt but that it not really an electrical requirement. Then I worked through the power supply, tidying up the wiring and removing, sleeving and resoldering any componet leads that could short.

Then working backwards through the stages starting with the audio output. I made layout diagrams, desoldered everything, cleaned up the tags (removing cut-off wire ends, etc) and reassembled it. Fitted a few NOS resistors when the originals were too mangled. And replaced 'that capacitor' anyway.

After doing the audio/detector stages I moved back to the IF amplifiers. The first problem was that one of the IF transformer mouting nuts was missing. The stud (fixed to the transformer can) was 3mm diameter but a normal M3 nut didn't fit. In the end I re-mounted the rectifier valve holder using normal M3 nuts and bolts and used one of the original nuts thus freed to fix the transformer. Then the IF gain control needed repair, the shaft was cut too short for the knob to fit. As I discussed in another thread here, it's a 10k reverse-log taper pot. The original track together with the spindle/slider from a pot in my junk box made an electrically correct part with a long spindle.

Alas the knob was designed for a 6mm spindle, not a 1/4" one. But it was easy enough to drill the knob out to 6.4mm, whereupon it fitted perfectly.

The RF/Mixer/Local Oscillator stages had been totally mis-wired, it wasn't worth making a diagram of what was there.I removed the components and re-wired according to the circuit diagram. In the process I found the RF amplifer control grid series resistor (should be 47 ohms) was a 47nF capacitor meaning said grid had no DC path to anywhere. And there were a couple more similar errors.

I didn't do much on the coil pack as I didn't want to upset the alignment. I did replace the tatty wires that connect it to the rest of the receiver and also sleeved the wires of the 33 ohm resistor in the oscillator circuit.

The BFO unit had not been touched so I left it alone.

Next I refitted the coil pack and BFO and connected them all up. Put the valves back in, connected a length of wire as an aerial and a small speaker and powered it up.

I was not expecting it to work, after all I'd removed and refitted just about all the components and must have made mistakes, right? Wrong!. After warming up, I could receive signals on all the bands.

As to whether it is 'finished', I think it could do with re-alignment, but I don't have a suitable RF signal generator. That will have to wait. But I am still pretty pleased with getting it working first time.

Last edited by TonyDuell; 21st Dec 2018 at 2:57 pm. Reason: Added a bit I'd forgotten
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Old 21st Dec 2018, 4:15 pm   #2
Andrew2
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Default Re: Trio 9R-59 Shortwave Receiver

Wow Tony, that sounds like it's been brought back from the brink!
Is it the original 59 or one of the D or DS types? I bought a DS new in 1973 and it was my main receiver until I bit the bullet and got a used Trio R1000, a much better radio.
The main problem with the 59 DS was tuning drift, especially on the higher bands. It never seemed to fully stabilise, even after long periods of warm-up.
There was no built-in speaker, so I put one in, only to learn the unsettling effects of microphony in the local osc!
I gave it away in the early 80's to a budding young Amateur, but never heard anything further from him....
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Old 21st Dec 2018, 4:51 pm   #3
TonyDuell
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Default Re: Trio 9R-59 Shortwave Receiver

It's the original 9R-59 (no suffix letters).

When I got it, somebody had bolted a speaker to the back (screws through the cooling slits, so no real case damage. I removed it, I like to keep things reasonably original. For testing it, I used an little PC-type speaker unit (no internal amplifier) that I bought in a charity shop. Quite useful for jobs like this.

I've taken some before/after photos, I'll try to upload them sometime but probably not until the new year.

As to the design of the set, it's a bit better than a domestic set with SW bands, it does have separate local oscillator and mixer valves, it has a BFO/Qmultiplier. But just a simple diode detector. And no HT voltage stabiliser. I feel it's a reasonable SW 'broadcast' set but not really a communications receiver. On the other hand it was cheap and fun to restore and I like taking on 'wrecks' and getting them back to rights.
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Old 21st Dec 2018, 8:30 pm   #4
dave walsh
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Default Re: Trio 9R-59 Shortwave Receiver

That sounds like a very thorough and painstaking restoration Tony. The photos will be welcome. I get a bit confused with these sets but your reference to the HE-30 suggests you have the version with a horizontal tuning scale. I've referred to this in the past on a thread that Andrew responded to as well ie Trio 9R59 "Got At"... by SHORT WAVER 22/1/11 [p7]. As I understand it the D or DS designations refer to the version with the small round dial like the one I have or perhaps I'm just confused? I don't think I got a direct response back then

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Old 21st Dec 2018, 11:17 pm   #5
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Default Re: Trio 9R-59 Shortwave Receiver

If my memory serves me true, this radio was also distributed in a kit form: KT-340.

Al.
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Old 21st Dec 2018, 11:43 pm   #6
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Default Re: Trio 9R-59 Shortwave Receiver

This was the KT-340.
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Old 22nd Dec 2018, 12:21 am   #7
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Default Re: Trio 9R-59 Shortwave Receiver

A good effort!

A good set to get going on, though not so good to use.
When you get a sig gen, it'll be a good candidate to practice alignment on... and whither then? HRO? AR88? something off the beaten track? or straight to an RA17?

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Old 22nd Dec 2018, 5:58 am   #8
TonyDuell
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Default Re: Trio 9R-59 Shortwave Receiver

This is the original 9R-59 with the horizontal tuning dial. Actually 2 dials one above the other, the main dial and the bandspread (the usual electrical arrangement of 2 variable capacitors in parallel).

The KT-340 looks identical from that photo and the features match up. Mine is a 9 valve set too. Mostly B7G base with an octal-based rectifier. I am a little bothered by the description of the 'semi-kit'. If the 'RF section' is what I call the coil pack I can understand it. If it means the RF valves and maybe the IF amplifier have been wired then there is little more to do AND it's a lot harder to work on the audio section when the coil pack is in place (which is why I removed it when working on my set).

As for what next (in terms of radio), probably some domestic sets. I have a few to work on. But most are AC/DC types so the next job is to make an isolating transformer unit.
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Old 22nd Dec 2018, 8:26 am   #9
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Default Re: Trio 9R-59 Shortwave Receiver

It may be worthwhile modifying the power supply to the the local oscillator with a simple stabilizer circuit to see if you can improve the poor drift performance?
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Old 22nd Dec 2018, 8:58 am   #10
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Default Re: Trio 9R-59 Shortwave Receiver

Quote:
Originally Posted by dave walsh View Post
That sounds like a very thorough and painstaking restoration Tony. The photos will be welcome. I get a bit confused with these sets but your reference to the HE-30 suggests you have the version with a horizontal tuning scale. I've referred to this in the past on a thread that Andrew responded to as well ie Trio 9R59 "Got At"... by SHORT WAVER 22/1/11 [p7]. As I understand it the D or DS designations refer to the version with the small round dial like the one I have or perhaps I'm just confused? I don't think I got a direct response back then

Dave
Yes, the D and DS are the later ones, which are completely different. They have a large central tuning knob with a concentric BS knob and two small rectangular windows, one for main tuning and one for BS. Despite the presence of a stabiliser in the DS, it still drifted and there was chronic 'pulling' of the local osc on strong signals on the higher bands which made SSB reception interesting unless you kept the RF gain low. Not my photo.
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Old 22nd Dec 2018, 2:23 pm   #11
dave walsh
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Default Re: Trio 9R-59 Shortwave Receiver

Thanks very much for that Andrew. You've shown the one I have. I wasn't even sure any one understood what I was on about in 2011 When I mentioned "small round dials" I actually meant square but with curved content. I think people might have bought one or the other type without being aware of the change in design and they do look completely different! The popular series of articles in SW Mag, re mods to improve performance, relates to the later version. As Tony said these "slide rule" sets look good but were pretty basic really [and not at all cheap]. There were lots of them about under different brands names in P Wireless.

The HE-30 was probaly top of that range with the two dials. I've a couple of "single scale" sets here in the Bexhill garage /office, a Veritone DX MATE CR150 and a Monarch Ham-1. I recall my friend Pat improved the BFO injection on the latter considerably by just soldering in an open ended small piece of wire at the oscillator grid stage that was effectively a capacitance he could move about to optimum effect!

Dave

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Old 2nd Jan 2019, 8:58 am   #12
TonyDuell
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Default Re: Trio 9R-59 Shortwave Receiver

I've put a few photos of the restoration here :

https://www.flickr.com/photos/tony_d...57699337512700
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Old 12th Jan 2019, 8:25 am   #13
Phil G4SPZ
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Default Re: Trio 9R-59 Shortwave Receiver

Tony, congratulations on that painstaking rebuild. I can just imagine your delight when the set came to life after all that work.

I have the later DS version which took some work to get it fixed, and it too suffers from the same tuning drift problems that have been mentioned. The HT voltage stabilizer makes no difference at all. After much investigation, I discovered that the set is actually very sensitive to temperature changes and mains voltage fluctuations, and I think it’s more to do with the heater voltages than anything else.

Despite all its failings, this set is still strangely appealing, and its performance on Medium Wave alone make it a good set to have. Well done!
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