1SV153 varacap diode: need source or sub

[Marc Mallett]

Hi Folks,
I am looking to rehab my Kenwood TS440S/AT and one of the areas where a rather poor choice of anti-microphonics media was used has quite a number of these diodes. They appear to be a Toshiba discontinued part, and from the article I read on doing the rehab on the radio suggests getting a small handful and having them handy (perhaps they are delicate?) when removing the anti-microphonics material.
Has anyone here done a similar rehab to their rig, and if so how did you fare in the removal of the undesired substance? I've no idea how difficult the removal is of the brownish substance Kenwood used (it becomes moisture absorptive and then the dreaded "display full of dots" syndrome begins as some or all of the VCO's become inoperable).
I don't want to start on this until I have something suitable in hand to replace or sub the fragile parts. Any help the readership here could provide would be very much appreciated! This radio has been my only HF rig and now I'm down until I can dig into this problem.
Thanks!
de Marc N9KHI

[Marc Mallett]

I had some time today to do some searching and oh man is that 1SV153 diode a tough one to find! There will obviously be some substitute required as this part is no longer manufactured by Toshiba.
If I go to the trouble of finding an affordable and obtainable substitute but have to buy a large minimum, are there enough TS440 owners here that have the "all dots" syndrome and want to get their rigs up and running? The articles I read on rehabbing the TS440 says that these diodes are fragile and prone to breakage during the removal of Kenwood's poor choice of anti-microphonic potting material that causes the whole "dots" problem. Now, I myself have yet to even open my radio up until I find out if/when I can get some of these diodes in case I ruin a few. If someone else has done a rehab on their rig, please post your experiences here as it seems like every TS440S ever made will someday exhibit this problem.
Marc Mallett, N9KHI

[Marc Mallett]

I found a sub that will work, but the leads will be different. The Toshiba 1SV214, in current production, is electrically an exact replacement except in a surface mount package, which essentially is the same case style with SMT leads vs the longer thru-hole leads. Wht I did was to go to a local hobby shop and get a small piece of .005" thick brass sheet and, using a paper cutter shear, slice off strips of brass that are the width of the original 1SV153 leads and after soldering on the "leads" cut to match the length of the original part. This could all be done with ordinary scissors but the cut is not as clean. I soldered the surface mount part leads to the brass strips, which now make the part a physically drop-in replacement. A bit of work, requiring a steady hand and good eyesight, but quite acceptable results. Careful, the brass is a bit sharp after cutting.
This is the solution I pursued. I only broke one of the original parts in the reworking of my radio, due in part to using a solvent to remove most of that nasty Kenwood potting compound vs scraping.
Along with the above, bee's wax makes a perfect moisture-proof replacement potting compound, and allows for a rather nice appearance after the rework is complete. When I performed the alignment procedure per Kenwood's service manual, very little touch-up of the VCO stages were required, and the replacement varacap diode is operationally indistinguishable from its predecessor.
Hopefully this helps some folks out and you can get your rig back on the air too!
73 es cul de Marc Mallett, N9KHI