Garey, Even thought I had spontaneous healing of my TR7 per our e-mail discussion, I opened up the rig and did some voltage tests. Rig in SSB, all boards installed.
Pin spec measured 1 -5V -3.43 2 +25 23.3 3 gnd 4 AM 4.99 5 RTTY 7.01 6 CW 4.31 7 LSB 6.26 8 USB 3.83 9 DCin 13.53 10 +10VDC 10.01 11 +5V 4.90 The 24VDC line stayed solid as I moved the bandswitch and up down buttons. Per the drake service dept alignment procedures, pin 2 should measure between 23.25-24.0. Assuming my meter is accurate, that voltage is very close to being out of spec low. Maybe a weak/leaky C2110? I could not get to the input of U2103 (24V regulator) without pulling the DR7 board. Pulled it and installed probes and then reinstalled the DR7. Input to the 78c24 was at 27VDC immediately after turning on the rig, and then climbed to 32-35 volts w/i about 10 seconds. As I recall the 7800 family of chips need 2 volts to regulate, so I think input is w/i spec even at turn on. When switching the bandswitch, it made the input voltage move, but never under the 32 volt level. Caveat, using a DVM so it may have "spikes" that I was not seeing. After this, I pulled the DR7 and replaced it with the service kit "jumper logic board". Basically had the same results with it in place of the DR7 board. TNX es 73, Ron --- On Mon, 1/25/10, Garey Barrell <[email protected]> wrote: > From: Garey Barrell <[email protected]> > Subject: Re: [Drakelist] TR7 acting strange > To: "Ron" <[email protected]> > Date: Monday, January 25, 2010, 9:56 AM > Ron - > > Definitely sounds like marginal VCO locking. > > The bands from 160 - 20M will all wander around 17 > MHz. 15 and 10M > bands will wander around 34 MHz. > > An "open" AUX-7 position will result in an unlocked VCO, as > will pushing > the FIXED RCV button in. > > First step is to check that +24V DC supply bus. That > is the most likely > cause of this, i.e., "random, occasional, loss of lock" on > both PTOs. > Certainly there are other possible causes, but that little > transformer > core is a problem, and the "super glue" that Drake used to > put it > together is letting go (after only 40 years or so). > Easy fix, just glue > it back on. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement > CDs > <www.k4oah.com> > > > Ron wrote: > > Garey, > > I started to look at the TR7 last night. First > was to see for sure what was going on frequency wise. > Turned it on, 80 meters, where I had left it and it was > fine. 2.5 then 1.5 wondering 17xxx.x 1.5. Back > to 80 meters fine, and of course everything else was fine > too. So then I went back down to 2.5 and 1.5, they too > were fine now. So I thought maybe temperature or time. > Could not get it to fail after several hours. > > > > Got to playing and went to aux settings. They > were fine with the band light lighting if I was not in the > correct band. Then I went to an open aux location and > got wondering 17xxx.x. I can not remember it that has > always been that way or not. Looks like it could be > correct given the "block" diagram of the rig in my head. > > > > So I know it sounds like VCO/PLL issues, which > voltages are most likely. But, is there anything in > the bandswitch that exercise might cause to "clean > up"? Or am I in for what looks to be a PITA > intermittent? > > > > Also, I have looked for how my TX is open. The > motherboard out of lock trace is not cut, and the Q9001 > collector on the DR7 board seems in tack. Maybe I just > missed how they defeated Q9001. Is there something > with the aux board that also somehow "opened" the TX? I > thought it was only for the modules in aux, not the whole > TX? > > > > Thanks in advance. Also thanks for being an anchor for > this list. Your knowledge and willingness to share that > knowledge is a tribute to the real meaning of Ham Radio. > > > > 73, > > Ron WD8SBB > > > > --- On Sun, 1/24/10, Garey Barrell<[email protected]> > wrote: > > > > > >> From: Garey Barrell<[email protected]> > >> Subject: Re: [Drakelist] TR7 acting strange > >> To: "Ron"<[email protected]> > >> Cc: [email protected] > >> Date: Sunday, January 24, 2010, 4:40 PM > >> Ron - > >> > >> You may need to recheck your frequencies. > ~17 MHz is > >> the "target" frequency for the Lo Band VCO > (through 20M), > >> and 34 MHz for 15 and 10. This is where the > VCO's > >> settle when unlocked. > >> > >> First thing to check is the +24V DC supply. > This > >> higher voltage is used for the Loop Filter and > VCO > >> steering. If the voltage is low, check that > "E" core > >> on the DC/DC converter transformer on the little > power > >> supply board. > >> > >> There are other possibilities, but this is a > start. > >> Unless the transmitter has been modified, it won't > transmit > >> if the VCO is unlocked. > >> > >> 73, Garey - K4OAH > >> Glen Allen, VA > >> > >> Drake 2-B, 4-B, > C-Line& TR-4/C Service Supplement > >> CDs > >> <www.k4oah.com> > >> > >> > >> Ron wrote: > >> > >>> Got a strange one going on. Finished and > 80 > >>> > >> meter net and was headed to 40 to listen to the > Drake tech > >> net. On 80 meters it work find. But > when I go to > >> other bands, the display shows incorrect > frequencies. > >> Also on using the up/down buttons it will go into > strange > >> frequencies as well. > >> > >>> 1.5 show 1759x.4 and counts up slowly > >>> 2.5 same as above > >>> 3.5 80 meters okay and transmits > >>> 5 shows 1414.x > >>> 7 shows 3415.x14 displays okay > >>> 21 shows 17415.x > >>> 28 ok > >>> > >>> I did not go further and attempt to TX for > fear of > >>> > >> further injury. > >> > >>> It would appear the VCO/PLL are messed up, but > why > >>> > >> such strange combinations? > >> > >>> First thing will be board removal and > reseating unless > >>> > >> someone has a specific I should be looking for. > >> > >>> TNX es 73, > >>> Ron WD8SBB > >>> > _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
