UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

DMcMahon · 10th Oct 2020, 9:08 pm

Forgot to mention that during previous investigation into the ticking noise that grounding the input of the PB/Record head socket at the amplifier (i.e. tying down the floating input of the 0.05uF EF 86 Grid coupling capacitor) stops the noise/valve from oscillating.

Checked some more of the main components in the amplifier. Replaced the two 50uF/12V electrolytics for the 2 cathodes of the ECC 83, used NOS 47uF/16V. One of the originals had high ESR and the other one was totally open circuit. Also replaced 4.7kOhm resistor that was in parallel with the O/C capacitor, it was reading around 8k

Replaced (with new 0.1uF/600V Poly) the 2 remaining 0.1uF Hunts capacitors, one was a little leaky, the other a lot. One was on the 1 7/8 ips equalisation circuit , the other on the EM 87 Magic Eye Control grid.

At least 4 resistors I will replace later when correct values obtained, as they were around at least 30% higher that their stated values (they were 10% silver banded tolerance).

10th Oct 2020, 9:08 pm	#51
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,603	Re: Brenell Purchases Forgot to mention that during previous investigation into the ticking noise that grounding the input of the PB/Record head socket at the amplifier (i.e. tying down the floating input of the 0.05uF EF 86 Grid coupling capacitor) stops the noise/valve from oscillating. Checked some more of the main components in the amplifier. Replaced the two 50uF/12V electrolytics for the 2 cathodes of the ECC 83, used NOS 47uF/16V. One of the originals had high ESR and the other one was totally open circuit. Also replaced 4.7kOhm resistor that was in parallel with the O/C capacitor, it was reading around 8k Replaced (with new 0.1uF/600V Poly) the 2 remaining 0.1uF Hunts capacitors, one was a little leaky, the other a lot. One was on the 1 7/8 ips equalisation circuit , the other on the EM 87 Magic Eye Control grid. At least 4 resistors I will replace later when correct values obtained, as they were around at least 30% higher that their stated values (they were 10% silver banded tolerance). Attached Thumbnails Last edited by DMcMahon; 10th Oct 2020 at 9:17 pm.