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The R7 and TR7 use Molex tin plated pins in the plug in printed circuit boards. Tin to tin contacts oxidize and become high resistance. For those to have corrected problems in the 7-line equipment by unplugging and plugging back in the PCBs that cleans the oxide on the tin contacts and corrects the problem for awhile (don't forget to use DeOxit ProGold when doing so). A more insidious problem is when high current has to pass through these tin contacts. Oxidation, higher resistance then heat and board failure. For those who have had the unfortunate experience with your R7 12 VDC regulator board, you know what I mean. If your board does burn up, just replace with IC regulator in place of power transistor on the heat sink on the back of the receiver. If your regulator board is still working, highly recommend replacing the tin plated Molex connectors on the regulator board with connectors having gold plated contacts. That will reduce oxidation of the contacts and failure of the PCB. Collins used all gold plated contacts on the KWM/HF-380 connectors. I've never had a connector contact problem with my KWM-380 in 30 years. Drake was saving a few dollars on each 7-Line radio by using all tin plated connector contacts and created a reliability problem for us years later. 73, Paul W5NTQ

Curious if anyone has done any of these mods to their TR-7 as suggested by Scott/N7NB? Dug out the "Family Affair" book the other day and saw the list of mods, same as the article that Jim S posted. The audio filter sounds like a no-brainer as I find myself engaging PBT just to tone down the harsh highs. Would love to add true QSK as well although looks challenging. -- Craig/W8CS Greenville, SC

The following items have been added to the Files area of the [email protected] group. /R7 Files/Drake_R7_PS_Early.pdf /R7 Files/Drake_R7_PS_Late.pdf By: Jim Shorney <jimNU0C@...>

Looking for the SPR-4 preselector knob. Can anyone help? Peter OZ8CTH

The situation: When I transmit on CW and let up the key, the meter goes to the power out during key-down, as normal. When I let up the key at the end of sending, the meter swings hard to the right when using shorter delay settings, controlled by the CW delay "knobette". If I use a longer delay, there's nothing unusual happening with the meter. Listening on my IC-7610, and watching the spectrum, there is no RF being indicated by either the receive audio or by the spectrum display. This set has always worked like this since I've owned it. I would think that if this was a real spike, I would see RF out. Listening on two other receivers, not a peep when key is opened. Could something in the receiver be putting a voltage onto the receiver's meter circuit, which gets switched on when the TR7A returns to receive? Steve Wedge, W1ES Time flies like an arrow. Fruit flies like a banana. Sent with Proton Mail secure email.

I currently have a Drake R4A receiver and T4XB transmitter for sale on my for sale webpage. Click link below to view the R4A and T4XB. Drake Gear For Sale 73 Mike W5RKL https://www.w5rkl.com

While listening to my TR-4 late yesterday evening, I noticed that the lower bands had a prominent, continuous "swish-swish-swish" noise at about 2 or 3 Hz. I checked and I was also getting that on my R-390 so, thankfully, it didn't appear to be a new problem with my TR-4. Are others on the list hearing this as well? It's noise that I don't recall hearing before and, possibly as a result of it, I didn't hear very much activity on the lower bands either. Just curious. Thanks, Barry - N4BUQ

I oftentimes think that we take our favourite radios from the past as having survived because we have lavished lots of attention on them and have dutifully replaced old capacitors, etc.. Then I buy a C Line that hadn't been powered up since 1984, I bought from a friend today a C Line with an etek FR-4 that hadn't been powered up since 1984, I bought it at a price commensurate with being dormant for 40 years and it was a great deal. Firstly, the e-tek needed nothing. By the 1980s, we had really mastered the art of making capacitors that last. The unit is nearly within spec. I can't get to direct measurement and that may be due to a dirty switch. Direct mode switches off the convertor by grounding it. Perhaps the switch is a wee bit dirty. BYW, I have the original manual for this and I will eventually scan it to be shared with anyone who wants a copy. The T-4XC puts out 130+ W on 20m. The switches are incredibly dirty but finding a band to test output on confirms that the finals are in good shape. I used my bench supply. There's no need for using a variac for any 4-Line transmitter. The only can cap is not anywhere near HV and it it fails, it won't take anything with it. The R-4C is a mid-later production unit. It has 5-position filter switch, 6EJ7 mixers. I have also found that it has a few Sherwood mods (audio amp, power supply, mixer and a lovely GUF-1 filter!). Brought it up over about an hour and a half. It's working but dirty, dirty, dirty! Some bands are better than other due to the dirty switches! Frequency on 15 MHz confirmed that the dial was set right-0n, and the calibrator was bang-on, also. The AC-4 has the end of the cord cut off, so I will be more caretul -- though the finals are in great shape, so I think someone cut the end off to force an examination of the supply, which I will do. The MS-4 should be fine. It's hard to wreck a speaker in one of these, as you can't push any pointy things into the cone... Forty years without being powered up. Yeah, the Jackson drives are sluggish as hell and the PTO's require maximum torque to turn. They're not seized but should be easily freed. These rigs can take some neglect, as long as you don't put them in an unconditioned space. If a cap blows up, I can replace it. Oh -- whatever I do with this, the GUF-1 won't be leaving my possession! Steve Wedge, W1ES Time flies like an arrow. Fruit flies like a banana. Sent with Proton Mail secure email.

Looking for a nice and clean SPR-4 front panel. Can anyone help? Peter OZ8CTH

I'm still looking into my TR-4's 9 MHz oscillator. Earlier, I said I could wrap a coil of wire around the oscillator tube (V16) and measure the frequency but apparently I was misremembering something because I tried that last night and I could not get the counter to trigger on anything close to 9 MHz so I just used a 10:1 oscilloscope probe which worked fine. Unfortunately, I am not able to get the oscillator exactly on 9 MHz. C130 will adjust it down to about 9.000280 MHz but I presume I should be able to swing the oscillator very slightly above and below 9 MHz leading me to believe the crystal has "drifted" upwards just a bit and because of this, I'm not quite able to get one of the filters to respond correctly. IIRC, the LSB filter will respond down to inaudible as I approach zero-beat with the calibrator; however, USB fades out long before zero-beat and I think that's due to the CO being too high. Any suggestions on a fix? I presume baking it might bring it back down but if that doesn't work, then I'd like to replace it. They're available new in that form factor (HC-49) but I'm not sure about what other characteristics I'd need to consider. I presume this isn't a series crystal and should have an appropriate load capacitance but perhaps other factors may need to be considered. Anyone know the specs for that crystal? Thanks, Barry - N4BUQ

I'm noticing that the HV from my rebuilt AC-4 is running quite high - on the order of 730VDC. I know that my line voltage is around 126VAC and if I run the AC-4 from an autotransformer, I have to dial that back to approximately 110VAC to see 650VDC output. I find that just a bit odd since the input voltage on the schematic shows 120VAC. I can reduce that input voltage with either a bucking transformer or I also have a rather heavy-duty transformer with multiple input taps where I can feed my line voltage across the 132VAC connection points and have 110VAC at the 115VAC tap. I'm just wondering why an increase of 6VAC from the original spec has the output voltage so high and whether that increase is detrimental. I realize the filament voltages are probably on the high side as well (I haven't checked those) but that may be harder on the tubes than the HV increase but I don't know that for sure. Any thoughts? Thanks, Barry - N4BUQ

Fellow Drake Enthusiasts, Here's my list with prices of what I'll have for sale and pickup at my QTH around Hamvention time. Cannot ship. Unable to bring to Hamvention due to health issues but I'm only about 4 miles from Greene County Fairgrounds. New in the box Drake RCS-4 remote coax switch $175. Shure 450D series II, new in the box microphone, $110. D-104 Final Edition microphone, new in display case, never used, $250. Hastings fiberglass hotsticks for POTA, Field Day, etc. new 35 ft $75, and used 44 ft $50. Jackite 31 ft orange windsock pole, used once to measure tree height, $50. Heath SB-200 linear, mint, with new PS upgrade, soft key, and faster changeover relay, $400. ME26 D/U professionally refurbished military millivolt meter, $60. Hospital grade isolation transformer, $30. Johnson Ranger, "8+" on outside, operation unknown, $75. Nye Viking (Johnson) KW Matchbox, "9+", with coupler for SWR meter, dark gray matches Drake, $300. New, pocket DTMF phone dialers, produces DTMF or single tone, for testing linears, etc. $5 each. If you want to buy any of these please let me know OFF LIST. 73, Evan, K9SQG K9SQG@...

Hi everyone. Haven't had much time for the TR7 due to ill health. However I have the transistor for the 10R line. I wondered what caused it to blow in the first place. I checked the 10R line,for resistance to earth with the test leads in both directions. It read 160 ohms. It looked a little low so I pulled,a few boards which used,the l8ne. if/audio, if filter, switch and 2nd mixer. One pulling the second mixer the resistance went to zero. Tried,another board and it was the same. No wanting to blow the transistor does anyone know if that resistance is correct? Thanks Mike G3ZCC

When I attempt to set the 9 MHz oscillator by listening to the sidebands (per the manual), each sideband sounds "different". It's as if I can get the "frequency" of the sound the same but the bandwidth of the sound is different. It's as if one sideband's filter is narrower than the other one. Does that make sense? I presume it's possible and that one or the other filter's shape is different (i.e. a narrower bell-shape than the other one). If that's the case, then is it an indication that there's something wrong with one (or both) filter that's making them sound different in this way. I know that may sound like a weird explanation of what I'm hearing but it's about the best I can describe it. BTW, 40M seemed terrible at my QTH today. I was hoping I'd hear the net with my TR-4 but I could just barely hear anyone today. Thanks, Barry - N4BUQ

Hi everyone,sad news. I traced the issue,finally, no 10R getting to the filter board, not even on the socket. Checked the 10R on the psu board, exactly 10.0v Removed The front panel and the two banks of switches. No 10R but 13.6 v. On A and B The switching seems,to work though. At a complete,loss now. Last gasp the circuit is hard to read where do the switches derive the 10 R from? Just in case I am missing something. It's the dustbin if I can't find the problem Thanks Mike G3ZCC

I recently picked up a set of C Twins at a hamfest and getting around to checking them out and I am having a problem with the R4C s/n 27279. When I first powered it up I got good strong audio but a few minutes later the audio would drop out and become distorted then it would come back strong a bit later. When the audio was strong it was crisp and clear. When audio drops out and becomes distorted and I have to turn volume all the way up to hear stations. Seems the receive is still good as stations who were S9 while in strong audio were still showing S9 on the meter after audio dropped. This happens in both SSB and CW. The change would happen when nobs like the band or mode were changed but also would happen randomly with no nobs turned or other contact. I cleaned the contacts and switches twice, tested the tubes (all tested good) but still swapped out with known good tubes, and changed the electrolytic capacitors using the Hayseed Hamfest cap kit all with no impact. Was not sure where the two 10uf 35V caps go in the Hayseed kit. I changed out what I believe to be the C175 but did not know where to change the other so still one 10uf not changed. Have tapped around on the chassis to look for loose connections with no effect. Have also probed around looking for cracked solder joints or cracked resistors and none found, at least yet. I am testing the unit as a stand-alone not connected with any cables to the T4XC except the antenna coming into the transmitter SO-239 then to the R4C through the shielded antenna cable. To make sure it wasn’t that connection or cable I put a wire into the antenna jack on the back of the R4C and connected it to my antenna and the problem was still the same. This issue seems to be evolving. Since I’ve been checking and testing, it now seems that the R4C is in the bad audio condition almost all the time and the distortion is worse. I noticed this gradually changed from about a 50% good audio/50% bad audio when I first got it to where it is now 100% bad audio condition. Any direction on what the cause of this audio issue might be and how to correct it is appreciated. Randal KG5IEE

Fellow Drake Enthusiasts, Per inquiries, I have prepared a partial list of what I'll have for sale and pickup at my QTH around Hamvention time. Unable to bring to Hamvention due to health issues but I'm only about 4 miles from Greene County Fairgrounds. Haven't priced things yet. New in the box Drake RCS-4 remote coax switch. Repair kits for L4B power switch; two complete with housing, one with just contacts. New in the box Drake KW dummy load, no optional fan. Shure 450D series II, new in box microphone. Fiberglass hotsticks 35 ft and 44 ft, new and used. Jackite 31 ft orange pole, used once to measure tree height. Heath SB-200 linear, mint, with new PS upgrade, soft key, and faster changeover relay. Medical grade isolation transformer. Johnson Ranger, "9" on outside, operation? Nye Viking KW Matchbox, with coupler, dark gray matches Drake. New DTMF phone dialers, produces DTMF or single tone, for testing linears, etc. If you're interested in any of these just let me know OFF LIST and I'll send you a complete list when done along with pricing. Bring your rain gear and enjoy Hamvention. 73, Evan, K9SQG K9SQG@...