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Mike. Watterson · 6th May 2019, 10:28 am

Try a separate speaker first.
Also check the main HT electrolytic. I forget if it's 4uF or 2uF. I've had strange issues because of that drying out.

I've a couple of CN429 as well as a few sets with a very similar chassis. Not heard what you describe though distortion or motorboating if that HT cap is dried out.

Also check the grid bias resistor between 0V and the -HT that gives the -ve bias for the DL96. The value can be +/- 20% without much change. If it's too high you'll get clipping (class B without the other channel) and if too low, there will be excessive DL96 anode current and transformer saturation then causes distortion.

I've used the mains transformer from cheap Argos clock radios etc as audio transformers for the DL91 / DL92 / DL96 series. The DL94 are often x2 output power so often the sets had a less fragile, larger transformer.

6th May 2019, 10:28 am	#2
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Vidor CN429 Lady Margaret rattling sound Try a separate speaker first. Also check the main HT electrolytic. I forget if it's 4uF or 2uF. I've had strange issues because of that drying out. I've a couple of CN429 as well as a few sets with a very similar chassis. Not heard what you describe though distortion or motorboating if that HT cap is dried out. Also check the grid bias resistor between 0V and the -HT that gives the -ve bias for the DL96. The value can be +/- 20% without much change. If it's too high you'll get clipping (class B without the other channel) and if too low, there will be excessive DL96 anode current and transformer saturation then causes distortion. I've used the mains transformer from cheap Argos clock radios etc as audio transformers for the DL91 / DL92 / DL96 series. The DL94 are often x2 output power so often the sets had a less fragile, larger transformer.