Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
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Emanuele, no need to reply to this, it is more for others that have an S-85. I don’t blame you for being fed-up with this radio, and giving up; we all have had that feeling, ?but for the benefit of others we wonder if ?yours is wired as per the schematic, or is it actually wired like I suggested it should be. You seem to be very good at tackling all this stuff, so if the wiring is apparently wrong at R65, you no doubt changed it and tried it again, I would think but I saw no comment on that point. ? I don’t have an S-85, but, for any others with an S-85: does it have the same alignment problem?, and poor sensitivity below 1Mc? ….and is it wired as per the schematic? as I highlighted before? ?I don’t believe they BUILD them using a schematic, instead they use a more practical physical wiring drawing; so it is hard to believe that they went out the door wired, and working incorrectly, but I have seen worse cases when I was in industrial electronics manufacturing, so impossible things do happen, then I had to find and fix the impossible out in the field. The big boss says “ship it anyhow”, and QA ?succumbs. Emanuele mentioned the S-99 is an exact copy in some detailed respects, so I looked and found that the S-99 eliminates all capacitors for the 1st RF tanks and the slugs for bands 3,4.? ?It is interesting that? they still list C3 with L3, but C3 itself has vanished.. ???typical copy and paste draughting [drafting if you’re in USA] ?? ? From: [email protected] [mailto:[email protected]] On Behalf Of Emanuele Girlando via groups.io
Sent: Sunday, February 9, 2025 12:56 PM To: [email protected] Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak! ? Guys, one of the reasons I wants to give up with this one is the poor design in the ANT RF circuitry. I noticed the schematic diagram anomalies, both the 1&2 bands wiring error and the fancy S1A-REAR layout, at the same time as Don did. I was shocked and disappointed by that. Days ago, while approaching the refurbishing project of my S-85, I did read that the SX-99 is a S-85 plus IF-XTAL and S-Meter. So I download the SX-99 schematic diagram to compare with but I discovered: 1.???? the 1&2 bands wiring error and the fancy S1A-REAR layout are? exactly the same in SX-99 as in S-85; that was shocking and disappointing for the second time (!!). 2.???? the ANT RF circuitry design has been completely reviewed in SX-99 eliminating TRIMCAPs and introducing a more useful antenna trimmer you can adjust while switching between? bands and/or connecting different antenna types input socket. My conclusion was that the S-85 ANT circuit doesn't worth any additional effort to be understood or further analyzed: The Hallicrafters it self changed its design in successive projects.. Furthermore, IMHO, there is no point in having a ANT tuned circuit inside the radio when, in everyday use, you would have to retune it every time you change bands or the type of antenna connected to the radio. Consequently? I got the conclusion that leaving it as "wide" as possible sounds like a good choice. ? In the hope of modifying my S-85 by reproducing the solution found in the SX-99, I also checked if the coils part numbers were the same but, unfortunately, they are not. ? The only remaining test I want to do on this one is to align ANT and MIX RF stages with the chassis inside the cabinet. In other words I want to check if the service manual statement: ? ? should be read as: "RF alignment MUST be made with chassis in the cabinet. ...". ? Thank you all once again. -- Emanuele (IU1KNR). -- don??? va3drl |
don Root