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SPR-4 AF control
It is a fact that on the TR7 a minimum of audio is heard when the AF control is turned fully down. On my SPR-4 the minimum level of audio is more than just acceptable, so I wonder if there is a remedy to the problem or a thing one has to live with. I lifted the leads to the AF control and checked the pot with an ohmmeter. 49 to 3909 ohms from the wiper to one leg, 3793 to 30 ohms to the other leg. Peter OZ8CTH
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Resistor R111 and C145B
I've done some additional wire tracing and I believe I may have found the overheated resistor on the TR3 schematic. From my wire tracing in the TR3, Pin 11 on the rear power connector is the +250VDC power supply voltage. Pin 11 connects to R111. R111 connects to the positive terminal of C145B, 60ufd 250VDC capacitor, one of the 2 capacitors in the only can capacitor in the TR3. I've found a picture of the underside of a TR3 and the color band of the overheated resistor are ORANGE ORANGE RED SILVER which is 3.3K 10% and it's a 1/2W resistor. If C145B shorts to ground under voltage then that could cause R111, 3.3K 1/2W resistor to overheat. This would short out the +250VDC rail causing loss of receiver function, no audio, etc. If my Ohms Law math is correct, a shorted C145B would cause 75ma of current to flow through R111 at a power level of 18W. I = E / R "E" is 250 "R" is 3300 250 / 3300 = 0.075 amps (75ma) 0.075 x 0.075 x 3300 = 18W I have measured continuity from one lead of the overheated resistor to pin 11 on the rear power connector and see continuity. I measured continuity from the other overheated resistor lead to C145B and found continuity. Using an ohm meter doesn't show C145B shorted but that's because the battery voltage is too low to measure the short in C145B. Under +250VDC C145B could easily short causing R111 to overheat and loss of +250VDC voltage to other circuits. I have a few more measurements to take to be sure then I'll have to replace C145 can capacitor. 73 Mike W5RKL https://www.w5rkl.com
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Drake FF-1
I've seen this in the TR-4 manual but I don't think I've ever seen one: https://www.ebay.com/itm/314218762222 Thanks, Barry - N4BUQ
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R7 Multi-Vibrator Harmonics
3
My R7 is working well, it seems. I am now running it on DC voltage. The multi-vibrator runs at about 28khz after it has been running for a while. It starts at about 24 khz when the R7 is first turned on. With no antenna connected I can still hear the harmonics drift across a frequency on 40M. I don't notice them with an antenna connected. And of course, they get stronger as you go to the lower bands. Is this normal? Dan (W3DF)
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I went through the tune up procedure and everything looked good until I got to the last step and the plate current never goes above .1 on the plate meter. I have set the bias with the PS per the manual. I checked continuity on the relay (both TX/RX) - it was good on both tests and I see it engage on transmit. The system receives quite well - especially after tune up. Looking at the bottom it looks like all the electrolytic capacitors were replaced. The large electrolytic multi section was replaced by three capacitors under the chassis. All tubes test good. At this point I am stumped - unable to get any power out of it. One other odd thing - if you turn the TX gain up past about three ticks while receiving you can hear an oscillation tone. I have lots of test gear and have restored several other tube transceivers, receivers and transmitters so this is not my first "radio" LOL. TIA and 73's Don W. KD4APP https://kd4app.blogspot.com
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I'm working on bringing a Drake TR3 back to life. During power up I noticed smoke coming from below the chassis. I quickly powered the TR3 off. I turned the TR3 upside down, front panel facing me, and found a 1/2W resistor that had overheated. The picture below shows the location of this resistor. Does anyone know the resistor's value and where on the schematic it's located? The Yellow shaft is used as a pointer and the Black arrow is also pointing to the resistor. It's to the "Left" of the audio transformer and between the 2 small PC boards. I need to determine what that resistor is so I can find it on the TR3 schematic then track down what caused it to over heat. The TR3 was in "receive" when the resistor overheated. There was no audio heard in the speaker. The 8 pin remote VFO plug was in place with pin 2 connected to pin 8 as shown on the TR3 schematic (the RV3 was not plugged into the remote VFO socket). Any help would be appreciated. Please reply direct to my email address. 73 Mike W5RKL https://www.w5rkl.com
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Items sold from posting
Fellow Drake Enthusiasts, The D-104 Final Edition microphone and the Shure 450 version II have been spoken for from the list I posted on the reflector and the QTH.com ad. The other items are still available. 73, Evan, K9SQG
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Interesting post on setting TR7 8.05 oscillator.
Found this on zerobeat under Drake Mods by VE3EFJ: 8.05 MHz Osc Won't Net This oscillator is varicap controlled and is used in conjunction with the 13.995 fixed oscillator to develop the BFO. In doing it this way, there is little chance that there will be BFO leakage, or what leakage there is, can be controlled. There is a trimmer adjustment to net the 8.05 MHz crystal, but what the manual fails to tell you is that this adjustment is also affected by the trim pots for the injection frequencies for the BFO. If you try to set this trimmer up and it just won't trim, try an arbitrary setting of the trimmer screw and see if, say, on LSB you can get it to the proper frequency with the trim pot for that mode. Would this actually work? If the best one can net the crystal is say around 5.646 instead of 5.645 will the rig work correctly if the trim pots on the power supply board for USB, LSB, CW, RTTY and AM will all adjust to the proper frequencies? Seems a lot easier than trial and error padding of C1029. 73, Bill NZ0T
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I had a TR7 about 15 years ago and loved it but I sold it to help finance my K3 purchase, which I also love and still have. I acquired a TR7 today from an estate today with the PS7. It's S/N 2713. The thing was pretty dirty and will need a case repainting but seemed OK otherwise and the price was right. Here's what I have gleaned so far: 1. The PS7 doesn't work. I hear the transformer thunk when I turn on the rig and the fans on the PS and TR7 both come on but nothing else. The fuse is good and not blowing so I'll need to fix that at some point. 2. The rig came on fine with a different PS and seems to RX and TX fine but power out was around 170 watts and the ALC light was not coming on. I adjusted the control on the ALC board to about 150 watts on 20M at full drive and the ALC light now works but stays on no matter how low I adjust the drive. I know there's another adjustment for that on 10M on a diffferent board but I haven't gotten to that yet. Power doers adjust down to zero now. 3. The S-meter reads very low but signals sound fine so guess that's another adjustement I need to make. Forward and reflected hardly move the meter and adjusting the controls by the antenna socket make no difference. 4. Some good news is that all 4 filter slots are full which is great news for a CW op like me. 5. There's a big change in noise between USB and LSB looks like carrier balance is off. 6. The sidetone volume level is very low, I have to turn the volume control way up to hear it. I do have a PDF copy of the service manual. The big question is will I need the board extenders to fix all this and properly align the rig? If so wheer can I find some that won't cost me too much? My apologies in advance for the many stupid questions I'm sure I will ask as this project moves foward! 73, Bill NZ0T
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TR-4 - V11 12BZ6
3
The serial number for my TR-4 is 26040 which is presumably a Version 3 rig. According to Garey's TR-4 documentation, V11 switched from a 12BA6 to a 12BZ6 at Version 4 (S/N 27000) but my TR-4's V11 is a 12BZ6 (not just the tube but the label beside its socket as well). Is it possible Garey's chart is incorrect or am I misunderstanding it? I found the following comment from Garey as well: /g/DRAKE-RADIO/message/13132 I'm just curious as to the apparent discrepancy. Anyone know? Thanks, Barry - N4BUQ
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TR-4 Decreased Sensitivity on High Bands
28
Like other older things, my TR-4 (bless it's heart) is very hard of hearing on the upper bands. Signals and noise are quite strong on 80M and 40M but, starting with 20M, it becomes increasingly deaf to the point that on 10M, I have to turn the AF gain up almost fully open and, on 10M, the calibrator barely moves the S-Meter. On transmit, the problem is similar - not nearly as much output on 15 and 10 as the other bands so I suspect something common to RX and TX. The crystal oscillators are working just fine - strong enough output on the bands that use them and I've performed the alignment on the receiver. When trying to peak T1 (10M transformer), the S-Meter is virtually useless as an indicator as it barely moves off of "1" and I'm pretty sure it shouldn't be that way. Using my HP-410C, I've monitored the voltage at V7's control grid and the voltage consistently drops from lower bands to higher bands as I sort of expected it would. Should I be looking to V7 as the probable problem point or are there perhaps other circuits that are worth checking? I suspected this might be an AGC problem but not sure. Any pointers are welcome. Thanks, Barry - N4BUQ
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This is a bit off topic in some ways, in others it's something we have tossed around recently. I have an Icom repeater that appears to have a failed PA module, it draws 10 amps and has an output of 1 watt. It's a Mitsubishi RA55H4047M. I have talked to Icom, they have the part in stock for about $120. I have looked on line and I find this unit listed in many places other than Digikey, Mauser or Newark (They don't carry it). The images of the units all look identical including 'Japan" printed on the units as compared to the unit in the repeater but all sources that I can find seem to be coming from Asia, specifically China at price points between $38 and $66. The $64,000 question of course is do I risk one of these alleged "Genuine Mitsubishi" units or bite the bullet with Icom? 73, Ron wa7gfe
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Hello... I am new here. I have been looking for a document showing where the pin numbers referenced in the R7 service manual are located on the parent board. I understand such a document exists but I have had no luck locating it. Any help would be appreciated. Dan (W3DF)
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DRAKE USERS NET 7.238 MHZ.
Evan, K9SQG was our NCS for the Sunday Users net. There were 22 people checking into the net, and the users were using the following radios: A line: 1 B line: 1 C line: 3 TR-4: 4 TR-5: 1 TR-7: 5 Others: 7 Next week's NCS will be Ron, WB4HFN. 73'S, Mark, WB0IQK
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I'd like to pair a 2-NT transmitter with a 2-B receiver. The 2-NT manual says to connect the sidetone output to the grid of the receiver's audio amp or to the arm of the receiver's volume control (see below). Would this be a direct connection, or through a series capacitor, or ??? Since the 2-NT has a sidetone level control, I'm thinking I should connect the sidetone directly to pin 8 of the 8BN8 so that it's independent of the receiver's volume level. Thoughts?
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R7 12 vdc regulator board
2
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
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TR-7 Mods by N7NB?
4
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
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2 files uploaded
#file-notice
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@...>
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Wanted: SPR-4 preselector knob
Looking for the SPR-4 preselector knob. Can anyone help? Peter OZ8CTH
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TR7A Meter spikes
4
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.
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Image Name
Sat 8:39am
Sat 8:39am