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Old 25th Sep 2021, 12:20 pm   #1
Peterdee
Triode
 
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Location: Poole, Dorsetshire, UK.
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Default Trio 9R-59D restoration

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)
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Old 25th Sep 2021, 1:09 pm   #2
Andrew2
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Default Re: Trio 9R-59D restoration

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.
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Old 25th Sep 2021, 4:52 pm   #3
deswradio
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Default Re: Trio 9R-59D restoration

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
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Old 26th Sep 2021, 11:19 am   #4
Peterdee
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Default Re: Trio 9R-59D restoration

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
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Old 26th Sep 2021, 12:01 pm   #5
Station X
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Default Re: Trio 9R-59D restoration

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.

Quote:
Originally Posted by Station X View Post
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.
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Old 26th Sep 2021, 5:30 pm   #6
deswradio
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Default Re: Trio 9R-59D restoration

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

Best wishes
Des
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Old 26th Sep 2021, 8:02 pm   #7
Peterdee
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Default Re: Trio 9R-59D restoration

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
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