I did this mod yesterday to my S/N 4119 and am documenting it primarily for the parts number info. My unit had the REV B Control Board with the mod previously implemented by Elecraft (addition of 82 mH L1 across RP5 pins 7 and 10). The following applies only to REV B boards:
1. Remove L1 and insert a 2.2uF *non-polarized* capacitor in the same holes. I used a NICHION UVP1H2R2MDD1TD which fit nicely in the space for L1. I had to search for a suitable non-polarized capacitor so hopefully this will save time for others. 2. Cut the trace between C33 and C35. Check with a meter to make sure it's open. 3. Tack solder a 47 mH MURATA 22R476C between the pads for C33 and C35 (where the connecting trace was cut). This part is specified with internal resistance of 169 ohms which is key to the mod working properly (see below). I had to search quite a few different parts to find one with high internal resistance. 4. Lay the inductor on its side and be sure it is out of the way of the screw hole/standoff that attaches the Control Board. My K2 now has a very pure sidetone which will make zero beating much easier without harmonic distortion. 73, Bill W4ZV Sverre Holm-2 wrote >> My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite > different >> from the 180 ohm version used in the mod. Would a series resistor be > desired >> as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150 > ohm >> resistors on hand. Where is this resistor installed between U10 pin 7 and > the >> inductor or between the inductor and C33? > >> What type of capacitor would be best suited for this mod? My junk box >> only > has >> 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum >> capacitors. The polyester caps are rather large. A couple of the 2.2s in >> series would be 1.1 uF. > > > Darrell, > > I did the TF3MA sidetone mod some months ago on my K2 serial #2198 and I > am > very pleased with it. See my comments on > http://www.ac6rm.net/mailarchive/html/elecraft-list/2006-12/msg01043.html > where I wrote that "This mod really works wonders with the sidetone > quality > of the K2". I had done the sidetone upgrade to the 3000+ model previously, > but this latest change still was very worthwhile doing. > > You should add series resistance to the inductor. If I understand your > question right, the order, L+R or R+L, doesn't make any difference. I > would > try the 120 ohm resistor giving you a total of 120+62 = 182 ohms. Maybe > the > size > > I would probably have tried with the series combination of two 2.2 uF > tantalum capacitors in order to avoid putting the large 1 uF capacitor in > there. > > > > 73 > > Sverre > LA3ZA > > Unofficial Guide to K2 Modifications > http://www.qslnet.de/member/la3za/K2/mod.html > > -- > I am using the free version of SPAMfighter for private users. > It has removed 7471 spam emails to date. > Paying users do not have this message in their emails. > Get the free SPAMfighter here: http://www.spamfighter.com/len > > _______________________________________________ > Elecraft mailing list > Post to: > Elecraft@.qth > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com -- View this message in context: http://elecraft.365791.n2.nabble.com/sidetone-mod-now-works-tp395423p7581472.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
