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

G8UWM-MildMartin · 11th May 2019, 3:30 am

Part 2

Dummy load acquired.
TX tested. All OK.

Bought a TS-520 (original version) (collected from nearest city) in March.
Same faults!
(Unfortunately, despite heeding advice in service manual to avoid scratching VFO dial when removing the VFO, it put up too much of a struggle and had to be touched up)
Plus original PA valves (S2001, not S2001A as in the TS-520SE) had visibly distorted anodes and were goosed.
Replaced with NOS RCA 2 X 6146 and neutralised as per manual.
All OK now.

Then a TS-830S this week!

Advertised as very deaf on RX and little TX output.
Arrived well-packed and undamaged, with the advertised faults.
Main faults were on RF board: fractured joints on VCO input socket and 12BY7A valveholder and a couple on the other connectors, plus most of the carbon composition resistors high.
And the wafer switches were intermittent and needed de-soldering and dismantling to clean and lubricate.
Then some idiot re-installed all the wafers facing the wrong way round and had to repeat the process!
And the same carbon composition resistors across the HV electrolytics, the HV diodes, and the equivalent screen grid supplies as the TS-520 & TS-520SE, plus the ones on the PA board. The 6146Bs are OK and are GE, so probably replacements.
The antenna relay needed the TX contact cleaning and has seen better days, but seems OK now.
The Omron LZN4-12 relay on the AF board is intermittent. I have an LZNQ4-US-12 replacement on order (NF4EB-12 and MR24-12 are also suitable)

The shaft couplers on the bandswitch-to-PA-bandswitch, and Load are cracked and replacements on order ("6x6mm CNC Motor Jaw Shaft Coupler 6mm To 6mm Flexible Coupling OD 22x15mm" from eBay)

Remaining faults are RX deafness on 3.5MHz band (only) and vastly different settings required of the Drive control for TX/RX on 18MHz.
A bit of fun for next week!

11th May 2019, 3:30 am	#13
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Kenwood TS-520SE Transceiver overhaul notes Pt1 Part 2 Dummy load acquired. TX tested. All OK. Bought a TS-520 (original version) (collected from nearest city) in March. Same faults! (Unfortunately, despite heeding advice in service manual to avoid scratching VFO dial when removing the VFO, it put up too much of a struggle and had to be touched up) Plus original PA valves (S2001, not S2001A as in the TS-520SE) had visibly distorted anodes and were goosed. Replaced with NOS RCA 2 X 6146 and neutralised as per manual. All OK now. Then a TS-830S this week! Advertised as very deaf on RX and little TX output. Arrived well-packed and undamaged, with the advertised faults. Main faults were on RF board: fractured joints on VCO input socket and 12BY7A valveholder and a couple on the other connectors, plus most of the carbon composition resistors high. And the wafer switches were intermittent and needed de-soldering and dismantling to clean and lubricate. Then some idiot re-installed all the wafers facing the wrong way round and had to repeat the process! And the same carbon composition resistors across the HV electrolytics, the HV diodes, and the equivalent screen grid supplies as the TS-520 & TS-520SE, plus the ones on the PA board. The 6146Bs are OK and are GE, so probably replacements. The antenna relay needed the TX contact cleaning and has seen better days, but seems OK now. The Omron LZN4-12 relay on the AF board is intermittent. I have an LZNQ4-US-12 replacement on order (NF4EB-12 and MR24-12 are also suitable) The shaft couplers on the bandswitch-to-PA-bandswitch, and Load are cracked and replacements on order ("6x6mm CNC Motor Jaw Shaft Coupler 6mm To 6mm Flexible Coupling OD 22x15mm" from eBay) Remaining faults are RX deafness on 3.5MHz band (only) and vastly different settings required of the Drive control for TX/RX on 18MHz. A bit of fun for next week!