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Old 9th Feb 2019, 4:06 am   #1
G8UWM-MildMartin
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Default 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.
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Old 9th Feb 2019, 6:51 pm   #2
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Sounding good so far.
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Old 9th Feb 2019, 7:06 pm   #3
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Interesting! I have a 530, so lessons learned could well apply there.

For a while, I was tempted to let it go, but it's one of last "proper radios" with knobs instead of buttons, and I've decided to keep it.

Best of luck with your 520.

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Old 9th Feb 2019, 7:39 pm   #4
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

I would keep it and use it.
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Old 9th Feb 2019, 8:59 pm   #5
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Yes, thinking about it, it hasn't been powered up for a while. I'll dig it of its cupboard and hook it to the Variac .

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Old 9th Feb 2019, 9:54 pm   #6
G8UWM-MildMartin
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Thanks.
A quick look at the TS-530S service manual online has a photo showing the same type of resistors across the big electrolytics, and possibly on the rectifier PCB, but obscured by wires.
Since these are equalising resistors across the capacitors and diodes, failure of one would subject its component to overvoltage. As carbon composition resistors are notorious for failing even when unused, I'd definitely suggest checking them before powering up!
I trust your 530 has survived even better than my 520.
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Old 9th Feb 2019, 10:22 pm   #7
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Thanks for that info, but I'd actually powered it up before seeing your post (at least as far as the Rx and Heaters, so that would have put the HT on also). But, it did power up OK and seems to be working on the Rx side, though some Servisol might be beneficial.

I'll add checking (replacing) those resistors on the "To Do List".

I cannot remember when I bought it (many years ago), but it was secondhand from one of the big ham radio dealers. Seemed fairly good and had what looked like brand new GE 6146's in the PA, which tested very well indeed.

I see there's a Yahoo group for the 520/30 and 820/30, so I've just subscribed to that.

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Old 9th Feb 2019, 10:34 pm   #8
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Thanks for info. on the Yahoo group. I've just applied to join.
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Old 9th Feb 2019, 10:59 pm   #9
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

I just looked at the circuit diagram for those 6 off 470k resistors. Considering that the very nice Vishay resistors you've suggested are ~1p each, that looks like a very wise move; keep them coming .

Re the VFO, is that a simple air-spaced cap that does the tuning? I notice that the digital readout dropped out a couple of times at certain specific locations in the tuning range, hence the Servisol comment. That's happened since its been in storage.

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Old 10th Feb 2019, 3:14 am   #10
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Yes, it's a proper air-spaced capacitor with ceramic ends (in the 520, anyway).
The VFO isn't *very* easy to remove, needing the front panel and the PCBs behind and in front and a couple of "freezer bag ties" on the harness to be loosened and moved (at which stage the lamps are accessible) but it's OK, working methodically with the service manual, and there are some Youtube videos that give an overview ("Kenwood TS520" and "Kenwood VFO")( https://www.google.com/url?sa=t&rct=...9nAyIcQk0RPdVi, https://www.google.com/url?sa=t&rct=...c1SN3kjn--ePH8 although I don't necessarily agree with the rough treatment in the one that de-soldered the back wiper...
And another covered dismantling the gearbox, risking removing his fingers with an electric drill, then omitting how to re-tension the split (anti-backlash) gears on re-assembly.
They do mention the grease on the ball-bearings on the capacitor and the planetary drive hardening with age, though.
And they're very useful complements to the service manual, nonetheless.

Last edited by G8UWM-MildMartin; 10th Feb 2019 at 3:19 am.
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Old 10th Feb 2019, 7:19 pm   #11
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Thanks for that info. My VFO feels fine when tuned, but looks like there may be contact problems when the VC is close to either end of the range. Wonder what lube you used on it?

Back to the Rectifier Brd, part X43-1370-02 for the 530, coming off the 800V line is a line designated as 'HV' with R5,6&7 in direct series, each one being a 680k resistor. I haven't managed to find those in the parts list . I wonder if they too are composite resistors which may warrant attention?

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Old 11th Feb 2019, 1:29 am   #12
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

I used the usual Servisol Super 10 for the contact spring, also to loosen and flush out the grease, then lithium-based grease for the rear ball bearing, front balls and epicyclic drive balls and shaft.
The 680-K (your R5,6&7, my R2,3,4) appeared to be carbon film, but the associated 100K was carbon composition. I de-soldered one end of R6 to measure them all: they were all just high of their 5% tolerance, but within 10%. Work had stock of suitable 0.75-W 1% resistors, not used on any current product, so I changed them while the board was loose and the desoldering machine was on. It made no noticeable difference to the meter reading on "HV" in TX, so I didn't mention it earlier.
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Old 11th May 2019, 3:30 am   #13
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Default 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!
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Old 11th May 2019, 1:30 pm   #14
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Please keep us posted.I have a 530 which has no resistance when changing bands.(switch fault).

Also low o/put on tx and deaf on rx,which I believe there is res 33 or 39K that can cause this.Not easy access though.
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Old 12th May 2019, 2:07 am   #15
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Sounds like the plastic shaft coupler from the bandswitch to the rotary switch in the PA cage has cracked.
I have two plastic ones and a metal one on order. I'll report whether they are suitable.
The shaft pulls out through the front panel to give some clearance, but the coils on the RF board may still be in the way.
The RF board is a bit of a pain to remove, helped by displacing the frequency counter/display.
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Old 12th May 2019, 7:17 pm   #16
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

The Trio TS830 is a spendid rig which was deservedly popular, especially with contesters, in its heyday. Excellent both on receive and transmit. (superb on CW with the CW filter fitted). I bought one new in 1986, though lost interesit in amateur radio some years ago so I sold it, along with the matching AT230 ATU, (which will tune just about anything), the filtered speaker, the Low Pass filter, and HS5 'phones.

The TS830 sold really well for some years and they often crop up at rallies at very reasonable prices. Now more than 30 years old, so it's not surprising that some common faults and shortcomings have arisen, including the bandswith shaft coupler, but it's not difficult to fix.

There’s a picture of the original flexible plastic shaft coupler here, which illustrates how they fail over time:

http://www.lz5zm.com/kenwood-ts-830s...s-replacement/

Ken K4EAA in the USA, has specialised over the years in the repair of Kenwood TS-520, TS-520D, TS-520S, TS-520SE, TS-520SP, TS-820, TS-820S, TS-530S, TS-830S, R-820. He outlines the procedure for replacing the coupler with the least amount of hassle here:

https://www.k4eaa.com/couplers.htm

There’s also a youtube video here:

https://www.youtube.com/watch?v=sQV4Lt-fIy8

The original flexible plastic couplers were 15mm diam x 15mm long, fixed with four Allen screws. To remove the old coupler requires a long 1.5mm Allen key. EG:

https://www.ebay.co.uk/p/Draper-1-5m...d=323327230217

There seems no reason that the coupler has to be flexible or made of plastic. K4EAA can supply custom made rigid brass couplers which are smaller in diameter than the originals to makes replacement easier. (He can supply other parts too):

https://www.k4eaa.com/parts.htm

However, for customers in the UK, when shipping is added the cost is probably prohibitive. For anyone with access to a metalworking lathe it's not complicated to make replacements but 6mm shaft couplers can also be found on ebay, though usually with only one securing screw at each end rather than two. Flexible metal couplers for 6mm diam shafts are also available from a UK supplier but they’re 25mm long x 20mm OD:

https://www.ebay.co.uk/itm/254180503911?ul_noapp=true

Flexible plastic couplers for 6mm diam shafts (size of coupler 22mm x 15mm) are available here from a UK supplier:

https://www.ebay.co.uk/itm/6x6mm-CNC...wAAOSwW4tcRb05

A couple of other videos that might be of interest and help are here:

Adjusting the coil packs Kenwood TS hybrid transceivers with uneven receive/transmit peak on drive control:

https://www.youtube.com/watch?v=AAk5_LE5UF4

How to tune up the PA:

https://www.youtube.com/watch?v=bTVpQ18dn1o

Scores of mods, hints, tips and repair advice on the TS830 at mods.dk here:

https://www.mods.dk/index.php?ModelI...ioId=1-kenwood

Hope that's of help and interest.
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Old 12th May 2019, 7:48 pm   #17
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Thank you both for mention of this coupler problem,I will take a look.
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Old 12th May 2019, 9:31 pm   #18
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

David, you have identified both types of coupler I've ordered, and the sellers, exactly!
And the rest of your post is also of great interest, particularly about the coil pack.
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Old 15th May 2019, 12:34 am   #19
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Quick update:
Neither shaft coupler bought fits in the PA cage; they foul the neutralising variable capacitor and the hole, but both are suitable replacements for the one on the Load control which only had minor cracks to one hole and responded well to a drop of superglue and is OK on the bandswitch until a replacement arrives from China ("1Pcs 6mm Shaft Coupling Rigid Coupling Coupler Motor Connector + Spanner"), which is solid brass.

The RF board aligned perfectly well following the instructions in the user manual (Drive control at 12 o'clock, not peaked on RX as per the video) giving consistent receive sensitivity of the marker and CW output power across all bands ("CAR" carrier control needing to be progressively in with frequency to give ALC reading in range, as expected.)

No SSB TX was due to "PROC" switch needing some magic squirt.

The relay on the AF board seems to be behaving most of the time now, but will still be replaced when the new one arrives, and the board inspected for fractured joints while it is out.

I'm enjoying this so much I could be tempted to think about an aerial in the back yard.
(Haven't been on HF since operating G3GIZ/P on NFD in the early '80s, when this was made!)
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Old 21st May 2019, 12:43 am   #20
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Default Re: Kenwood TS-520SE Transceiver overhaul notes Pt1

Correction to previous post:
The black plastic shaft coupler arrived and does actually just squeeze in if compressed, and works perfectly. The headline description "OD 22x15mm" is wrong! It is 15mm OD and 22mm long, as stated in the text of the listing.
AF board relay now replaced and the adjacent zero-ohm link replaced by 100R resistor to protect the contacts when discharging C51 (I can't see the need to butcher the track to the wiper as in the "survival guide"). The original relay had quite a noticeable blast mark inside the case by the relevant contact.
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