Trio 9R-59D restoration

[Peterdee]

Hi all
I see there are a lot of posts on this radio already, so I guess if I was to plough through all of them all my questions would be answered, but being lazy I would be truly grateful for any answers and advice regarding my questions as I progress. When I first gingerly plugged the rig in, bringing the voltage up slowly, there was a loud scratchy hum, and nothing being received except some strong broadcast stations on AM, which were very distorted. The AF gain is very scratchy, so I sprayed it with switch cleaner, but no improvement. On advice from a colleague, I replaced all the electrolytics, and now the rig is receiving some signals, but rather weakly, and distorted. My colleague suggested checking for any volts on the AF pot. There is about 1.7v on the pot but only on function switch pos 5 (ssb/cw). Looking at the cct diagram could this be a leaky R30, or C32? I haven't done any of the voltage checks yet.
Any advice would be greatly appreciated.
Regards
Peter G0JJI (PeeDee)

[Andrew2]

Check on the grid of the o/p pentode. If there's even a trace of +v on there you've either got a leaky coupling cap or a duff valve.
Also check the cathode voltage on the o/p valve and compare it to the voltage in the cct diagram. If it's high there is too much current flowing through the valve. Don't run it in this condition for long as you risk blowing the o/p transformer.
BTW I haven't got the service sheet to hand so my comments are somewhat generic.

[deswradio]

Andy's right - check voltages round the output pentode. Coincidentally, I've almost finished restoring a 9R59DE and it's sitting on the bench next to me now. I too replaced all the electrolytics and quite a few of the others - the list I have is: c18 c23 c28 c32 c33 c34 c35 c37 c38 c40 c41 c42 c43 c44 c45. Quite a few were leaky. If problems remain, check voltages carefully (fortunately the service manual has voltages marked clearly). And make sure that the rotary switch contacts are clean. I'm surprised that switch cleaner didn't remove the scratchiness of the AF gain - make sure that you are getting cleaner on the carbon track.

Goof luck!
Des

[Peterdee]

Andy Des
Thanks for your comments. Yes, I have 4.5v on the grid of V8 but A and C are ok. Looking at the number of C's you had to replace Des, I reckon I have my work cut out for me, should keep me going through the winter. I take it the R's were ok then?
Peter

[Station X]

If you have 4.5V on the control grid of V8 you need to change the coupling capacitor C34 as a matter of urgency. Failure to do so could cause extensive damage to the set.

I know of at least two sets where this capacitor has failed.

Originally Posted by Station X

Voltage checking on these sets is very easy where the valves holders are mounted on PCB's. It's possible to check voltages from the top of the chassis. You just have to remember to count the valve pins anti-clockwise. Checking voltages on the output valve, a 6AQ5, showed there was +2VDC on the control grid, so I switched off. Naturally "that capacitor" in this case C34 a 0.01uF "oil" type rated at 630V was suspect. I snipped the end of it going to the control grid of the 6AQ5 and switched on again. The control grid now read close to 0V. Checking the voltage on the snipped end of the capacitor showed 13VDC, so it was definitely faulty. I decided that a new 630V capacitor would be over the top, so I fitted a 400V polypropylene component. The PCB construction makes component replacement very easy, no need to unwind wires from tags or disconnect other components. There was now 0V on the control grid of the 6AQ5 and the set sounded better, but not as good as I remembered it.

[deswradio]

I haven't replaced any of the resistors - yet - but it is a work in progress!

Best wishes
Des

[Peterdee]

Hi Graham
Thanks for that. I have ordered replacement cap's 34 36 and 38 so now all I have to do is remove the old ones. Managed to find suitable replacements on eBay, frustrating thing is no supplier had all three, so three separate packages coming through the door this week!
Peter

[Peterdee]

Update on my "restoration" of the Trio 9R-59D. Contrary to popular advice on this forum I have replaced most of the capacitors, except some of the ceramic "toffees" which look pretty indestructable. A few of the 'ceramic' ones looked a bit knackered so I replaced them and checking with my meter, they were indeed not giving the capacitance they should. The looked like fat wirewound resistors, not the usual type of ceramic capacitor. Before I did this most of the voltages were too high but now they are all in line w ith the given ones in the cct diagram. So, full of hope I connected antenna, switched on, and nothing on ssb/cw. Some AM stations coming through though. I don't know why, but something told me to have a tap around, and on tapping T1, the set sprung into life! CW/SSB coming in loud and clear. But now it's gone quiet again. I stuck the screwdriver in to tune for loudest signal, tapped again, resisted the temptation to bash with a hammer, but no joy. So to my untrained mind it would seem a fault with this transformer? I see there is a capacitor in the can, do I need to unsolder this and change the capacitor, or what?
In desperation
PeeDee

[Radio Wrangler]

If you're getting AM stations, but not SSB/CW, do you still get sounds when you tune across SSB stations? should sound rather 'quacky, the same as tuning across with AM selected. If so, your BFO isn't working, but did when you tapped its coil.

So have a look at the BFO first, and after that, I think this set has a separate product detector for SSB/CW which could also explain things.

David

[deswradio]

Are you happy with the performance on AM? If so, then as David says, looking at the BFO would be a good move. But I got the impression from your message that sensitivity was down on all modes.

I'd be reluctant to change the capacitor in T1's can. Check first for poor soldered joints around T1 and then start investigating for poor connections that may have been affected by a thump on T1 (i.e. almost anywhere). Some gentle poking and prodding and tapping round other areas of the circuit might lead to something. A common fault with these older receivers is of course poor contacts on the rotary wafer switches - switch cleaner would help here. I've very recently finished restoring a 9R59DE and one of the problems I had to deal with was very intermittent rotary switches.

Good luck - you're nearly there! Let us know how you get on.

Best wishes

Des

[Peterdee]

Hi David and Des
Guess what? I came into the shack tonight, switched on the Trio, and bingo! It's working again. Perhaps it just need a little rest?? Hard to tell how well it is working as the bands are pretty dead at the moment, but was able to receive ssb/cw where it was available. I guess it may have just been a bad contact on the switch, as you say they are a bit problematic. Anyway, the next job I want to do is change the two 9v lamps for led's. I see the supply to these is 6.3v ac 3A, same as the filaments. For led's I think I need about 3v DC and mA's. A dropping R in line would sort out the voltage, but how do I get DC instead of AC? Also there is space for another cct for a marker, which would be useful, as the tuning dial is not very accurate. I used my ft991a as a marker transmitting cw into a dummy load.
I guess I could get the info on the internet, but I thought I would sound you out first!!
Then there are a few mods to try, but that will be later.
I must say it's the first time I have done anything like this. I have built a few qrp cw transmitters, with transistors, and a couple of valve ones, but they are other peoples designs, I am not a radio engineer, but I found this more enjoyable.
The GQRPC are having a QRP valve weekend this weekend, so I hope to use the Trio for that.
Anyway, enough of my prattle, look forward to your comments.
Peter

[deswradio]

I's day that it really is worth getting to the bottom of the intermittent problem. Putting some switch cleaner on the rotary switches may well help.

Replacing the dial bulbs with leds - perfectly possible - but do you really want to? There's something attractive about incandescent lighting in these older receivers! But there are many ways of replacing the bulbs. It's probably worth using a bridge rectifier to generate the dc from the original bulb supply together with a series resistor to limit the led current (trial and error). No real need for any smoothing (but it can be added) because you will end up with flicker at 100Hz which you can't really see. You can also put 2 leds in parallel (anode to cathose and cathode to anode) with a series resistor - the leds (which are of course diodes) will do their own rectification.

A marker oscillator is really useful. When I first acquired this receiver (ages ago when I was a teenager!) I did the modification mentioned in the manual (I think), adding a 1MHz crystal. It adds a lot to the functionality of the receiver. I can dig out the details if you don't have them available.

It's a nice piece of kit. I used it for ages as my station receiver. It's nice to have it going again!

Best wishes

Des

[Peterdee]

Hi Des
Thanks for the info. Yes, I really like this radio too. Re the lights, they are bayonet 9v bulbs, like hens teeth. There are 6 or 12 v screw in types available, that is another option, if i can find the holders, probably not too much of a problem.
I have downloaded the mods from the American History site, they were published in the Radio Constructor magazine 1970 and 1971. Something to do later.
Onwards and upwards!
Peter

[raditechman]

I replaced the dial lamps with LED in my 9R-59D but made it easily reversable and the old lamps are inside ready to be use again if wanted.
At the same time, I added LED light to the S meter. I added a small full wave rectifier and resistor to get the low voltage DC
Main reason I did it was to give the mains transformer less current to supply so an easier life.
I also put a fuse in the HT supply.
John

[deswradio]

I just checked - the bulbs in my 9r59de are 8v 0.15a, fed by the 6.3v ac heater winding - it's likely that you can find led replacements that will just clip into the fitting (MBC) and then you don't even need to worry about extra components. Because those 8v bulbs are so underrun, they have never needed replacement...!

Best wishes

Des

[Peterdee]

Originally Posted by deswradio

I just checked - the bulbs in my 9r59de are 8v 0.15a, fed by the 6.3v ac heater winding - it's likely that you can find led replacements that will just clip into the fitting (MBC) and then you don't even need to worry about extra components. Because those 8v bulbs are so underrun, they have never needed replacement...!

Best wishes

Des

except one of mine

[deswradio]

Originally Posted by Peterdee

except one of mine

Ah! I now understand perfectly why you need the leds!

Best wishes

Des