UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Kenwood TS-520SE Transceiver overhaul notes Pt1

G8UWM-MildMartin · 9th Feb 2019, 4:06 am

I recently obtained a Kenwood TS-520SE HF Transceiver.
I nearly had kittens on receipt of a parcel of dimensions similar to the published size of the equipment!
On unpacking, the only damage was to the underside of the case, which was easy enough to hammer back into shape.
Whilst the case was off, I noticed it had the optional CW filter

I decided to check the HT electrolytics. They were not charged, and showed good for capacitance and ESR, with parallel resistance into the megohms.
Strange, as they have 470-K bleeders!
They were O/C, as were the ones across the rectifiers and another one across some other electrolytics.
They were carbon composition 0.5-W. Not ideal for having 450V across them for nearly 4 decades!
I replaced them with: RS Stock No. 683-5290 Vishay Part No. VR37000004703JA100 rated at 3.5kV 0.5W.
The VFO tuning drive was lumpy, so I removed the VFO and cleaned and lubricated it, replaced the (all) dead lamps with new (eBay item 253857115964, removing supplied leads and joining to existing wires with heat-shrink) and cleaned the front panel and knobs while they were removed.
It is now fully functional on receive, and the quiescent current and HT voltage on transmit are correct.

Part 2 may follow once I have a suitable dummy load.

9th Feb 2019, 4:06 am	#1
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Kenwood TS-520SE Transceiver overhaul notes Pt1 I recently obtained a Kenwood TS-520SE HF Transceiver. I nearly had kittens on receipt of a parcel of dimensions similar to the published size of the equipment! On unpacking, the only damage was to the underside of the case, which was easy enough to hammer back into shape. Whilst the case was off, I noticed it had the optional CW filter I decided to check the HT electrolytics. They were not charged, and showed good for capacitance and ESR, with parallel resistance into the megohms. Strange, as they have 470-K bleeders! They were O/C, as were the ones across the rectifiers and another one across some other electrolytics. They were carbon composition 0.5-W. Not ideal for having 450V across them for nearly 4 decades! I replaced them with: RS Stock No. 683-5290 Vishay Part No. VR37000004703JA100 rated at 3.5kV 0.5W. The VFO tuning drive was lumpy, so I removed the VFO and cleaned and lubricated it, replaced the (all) dead lamps with new (eBay item 253857115964, removing supplied leads and joining to existing wires with heat-shrink) and cleaned the front panel and knobs while they were removed. It is now fully functional on receive, and the quiescent current and HT voltage on transmit are correct. Part 2 may follow once I have a suitable dummy load.