"Jim Pruitt" <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Hello Ron.
Here is a link to Scott's comments about the article: http://www.dproducts.be/Drake_Museum/tr-7mods.htm I will paste them below then comment some more after the Prather comments that are copied from JM Cherry's great Drake web page: "Improving the Drake TR-7 by Scott D. Prather, N7NB (ex-KB9Y) Reversible Modifications Enhance Performance Please Note: The mailing address included on the first page of this article is no longer current. Please address all correspondence to Scott Prather at: [EMAIL PROTECTED] Abstract. The Drake TR-7 is an outstanding all-band, solid-state transceiver that was a trendsetter when it was unveiled to the amateur radio market in 1978. However, the TR-7 was not without its problems, some of which included: Poor receive performance below 1.5 MHz No full break-in (QSK) CW operation Compromised signal/noise ratio when using narrow CW filters High cooling fan noise, and the stock fan operates only when the radio is powered from an AC source My article, which originally appeared in the Summer, 1992, issue of Communications Quarterly, addresses these four problems with modifications that require no drilled holes, making them 100% reversible. Notes Improving the TR-7 is reprinted here in its entirety, and it appears on the Web with the permission of Communications Quarterly. I scanned the original 19-page paper and converted it into an Adobe ® PDF file. The size of this file is approximately 1.9 MB, so it will take a while to download if you are using dial-up Internet access. For example, at 28.8 kbps it took me about 14 minutes to download the file. Component Availability At the time that this article was written, all of the components required for these modifications were readily available. However, there are a few components that are currently difficult to obtain. The most difficult component to locate is D2005 (MA4P4002D), a stud-mount, high-power PIN diode manufactured by M/A COM. It's my understanding that this diode is no longer available from the manufacturer, and I've been unable to locate a diode that I'm convinced will function as a substitute. The MA4P4002D has the following specifications at 25 degrees Celsius: Series Resistance @ 100 mA forward current: 0.5 ohms Carrier Lifetime: 6 microseconds @ 100 mA forward current Voltage Rating: 200 Volts Power Dissipation: 15 watts Initially, my decision to use M/A COM's stud-mounted PIN diode was driven by the requirement to support 100% duty cycle operation, such as RTTY or SSTV. However, for low duty-cycle modes such as SSB and CW, I have successfully used the MA4P4002B axial-lead PIN diode with a small heat sink on the diode body. Unfortunately, this diode is not readily available either. Generally, any axial-lead PIN diode capable of dissipating about 5 watts and meeting the series resistance, voltage rating, and carrier lifetime specifications listed above should function in a low duty cycle application at the 150W power level of the TR-7. I will continue my search for a substitute, and I'll post my findings here. If anyone has a suggestion for a substitute, please send the information to me at the e-mail address listed above. The second component that's difficult to obtain is reed-relay K2001, manufactured by Magnecraft. I've been unable to locate a source for this part, however, it appears that an EAC P/N 20-1121-30 reed relay should work in its place. The primary difference between the original Magnecraft part and the EAC substitute is the lead pinout. The EAC relay has short in-line pins, while the Magnecraft part had longer leads which would permit a "triangular" PC pad configuration at each end. Also, the NC contact on the EAC part is on the opposite side of the relay from the Magnecraft part. However, minor redrilling of the PC board along with a jumper to the NC contact will solve these minor compatibility problems. Miscellaneous: A minor change in operation is required if a TR-7 is modified with my QSK card and subsequently used to transceive with a Drake R-7 receiver using the Drake 1548 cable. Because the QSK card RX Mute line only functions when the TR-7 is turned on, the R-7 will be muted if the "Mute" button is depressed and the TR-7 is turned off. To use the R-7 when the TR-7 is off, just release the R-7 "Mute" button. Errata: Although I carefully reviewed this article prior to its publication, in a project of this scope some errors are bound to occur. The known errors are: Page 22, Figure 3: Two minor labeling errors exist in this schematic. There are two capacitors labeled C2002, one connected to point "C" and the other to the drain of Q2002. The capacitor connected to point C should be C2006. Also, there are two capacitors labeled C2005, one connected to point "I" and one from L2002 to ground. The capacitor from L2002 to ground should be C2007. Page 24, Figure 6: The RX coax ground connection point (K) is shown incorrectly. This ground should be tied to the RF ground point that comes up to the NO contact of relay K2001. This point is just to the left and below the ground point (K) shown in Figure 6. Photo E on page 29 details the correct location for (K). Page 32, top left-hand column: The wires connected to points F and G on the QSK card were reversed. The list of wire colors should read as follows: 4) Connect the tan wire to point D 5) Connect the pink wire to point E 6) Connect the red wire to point F 7) Connect the blue wire to point G Page 37, Fan Control Parts List: Although it's not specifically stated, temperature-sensitive zener diode D4001 is in a type TO-92 case. Also, C4001 should be 1.0 m F, 35 volts, not the 25 volt capacitor listed. If anyone has questions concerning the modifications in this article or availability of components, please contact me via e-mail at [EMAIL PROTECTED] 73 Scott Prather N7NB" end of http://www.dproducts.be/Drake_Museum/tr-7mods.htm direct quote. Mr. Cherry also has the PDF of the Communications Quarterly article as a link just below the comments above but that PDF does not have the resolution on the pictures like the Comm Quarterly did and the reprint that John Loughmiller did in his book "R.L. Drake A Family Affair" but Scott Prather redrew the schematics in the book to make them easier to follow. I was unable to find the Magnecraft W104MIP42 for a reasonable price (as you also discovered). A friend (who is or was on this list at one time) redesigned the pc board for me so it is laid out for the EAC part that Scott recommends. It USED TO BE SOLD BY DIGIKEY and was used in some other very recent QSK articles (a VE ham had an article in QEX in spring of 2006 that used them) but Digikey no longer stocks it since EAC went to a rediculous minimum order for Digikey. I talked to EAC and they said they would sell direct to me but they had a $500 minimum (I think). The relay was about $8 from Digikey when they had them. Digikey lists the relay as "Call" so if a few of us call maybe they would stock a few more. Hold the phone! I just checked Digikey's web site and they have 80 of the EAC relays in stock right now at $5.75 each and stock number Z645-ND so they must have mananged to convince EAC to change their minimum but they do have them and cheaper than the ones that I got. As for the MA/Com Diodes (MA4P4002D) those are unobtainable! You can still get the MAP4002B from Richardson Electronics (they sell mainly to 2 way companies I think) and they were around $8 each when I bought my 4. They are in the DO style case like a 1N4007 diode (I forget what the DO# is) and so it will not disipate the power like the MA4P4002D but it is the same specs. I had asked Scott about using a 1N4001 as was suggested on another list I am on but Scott did not seem to think it would work very well so the MAP4002B is your best bet and is ok unless you are going to run RTTY or a similar mode that requires 100% duty cycle. Anyway I do have a pc board layout for the QSK board using the EAC relay footprint. You can also get a board set from Fred at Far Circuits. If I remember right the EAC relay had one contact swapped with the W104MIP42 so you could put it on the FAR boards and then redo those 2 contacts. The EAC relay pin out is in sort of a triangle (kind of like many pc board mounted pots) on each end so 3 contacts on each end but the center contact is moved in some but the outer contacts are in line. You did not mention the front end board but I had a little trouble finding the RSD-12V Aromat relays for that. Rich Measures AG6K - telephone, [805] 386-3734 at http://www.somis.org/ had them and are part of one of his amplifier mod kits. I think they were about $12 each. I also found a few on ebay later. I kept getting caught because the specs even on the RSD-12V say it is spst but it is REALLY SPDT. Even the legend on the relay does not show it but if you check the contacts you will find that it is indeed spdt! The RS-12V is spst but the RSD-12V is spdt. I hope that you find the above information helpful. Most of it comes from Scott Prather himself and posted on JM Cherry's web site at http://www.dproducts.be/Drake_Museum/tr-7mods.htm and some of the parts info was from my experience in trying to find the parts. I have done searches for some of the info before but usually my comments on this Drakelist in the past are what I find! Good luck and if I can help with more info or the Prather QSK pc board layout for the EAC style relay please let me know. Thank you. Jim Pruitt ----- Original Message ----- From: "Ron Wagner" <[EMAIL PROTECTED]> To: <drakelist@www.zerobeat.net> Sent: Tuesday, January 09, 2007 5:06 PM Subject: [drakelist] Specs for TR7 mod > > Ron Wagner <[EMAIL PROTECTED]> made an utterance to the drakelist gang > ---------------------------------------------------------------------- > Good evening all, > I am looking at the modifications in the Comm Qtrly mag Summer 1992 by > Scott Prather. Can anyone tell me about the specs on the reed relay > by Magnecraft W104MIP-42? Things like current, voltage, switching speed, > etc. > > I see there are a couple places on the web who have them for ~$70 which > seems a bit expensive to me. Maybe they are special enough to demand that > price, but I am thinking maybe not. > > I would like to try the QSK mod, but need to find that relay's specs and > see if I can sub something for the pin diode. I know that diode will be > a killer, so I am trying the relay first. > > 73, > WD8SBB ---------------------------------------------------------------------- Submissions: drakelist@www.zerobeat.net Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
