hallicrafters SR-2000 time delay relay?

Discussion in '"Boat Anchor" & Classic Equipment' started by WA6MHZ, May 20, 2013.

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  1. AF6LJ

    AF6LJ Ham Member QRZ Page

    I take it you can vary the preselector and see the drive level change...
    If so I wonder what the 8122 grids are seeing...
     
  2. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    I am seeing an output from the tubes, but can't access the grids due to plating. I need to make a measurement on the amplitude. But the problem seems to be no signal transferred to the antenna port. I need to put a tap on the antenna port so I can put my scope on that. i do see variation with the preselector so the Driver is working. Don't know how much drive though. Almost need a working unit to compare the levels with. I will try hooking it back up tomorrow. wish I could get at the relay.
     
  3. AF6LJ

    AF6LJ Ham Member QRZ Page

    The question had been brought to my mind because you said there was no variation in the plate current with drive.
    That indicates to me that you may not be getting drive to the grids.
    What you could be seeing in regard to the 200ma is just low bias / high idling current.
    If you had enough drive you could be able to get a dip in plate current even if the antenna relay was the problem, I believe.
     
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    I was thinking about the SR-2000 last night...
    I see the shield that is in place blocking access to the PA grids..
    If you don't already have some, I can supply some, get some cheap thin aluminum sheet. like roof flashing.
    I'll bring you a peace on Tuesday the stuff can be cut with a box cutter or almost anything.
    Make a peace to replace that shield, and punch small holes in it for access to the grid connection and any other points access may be needed. Tape them over until they are ready for use.

    Where the grid connection is bring out a very short peace of wire with some Teflon sleeting over it to attach a scope probe to, keep it really short. Tape up the aria around the hole to maintain the seal since that section of the chassis is pressurized by the blower. This should work for short periods of a few minutes for test purposes.
     
  5. W5WPL

    W5WPL Ham Member QRZ Page

    Sister Sue
    I think Pat may still have some of that preferred aluminum I sent him. But I think it's 0.0625 1/16"
    I still will help anyone with metal needs, as long as they pay postage and it's not copper that I have to buy.
    Just send dim. and a drawing of chassis or whatever. I prefer not to punch holes.
    73
    all
    W5WPL / Bill
     
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    That is good, this stuff I have is even thinner, it is about as thick as post card stock, good for all kinds of temporary applications.
     
  7. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Another LONG day wrestling this SR-2000!

    I decided to trace the Transmit string towards the Driver. Rewired the mic socket to be compatible with my 4 wire Hallicrafters mic I use on the SR-400.

    The Mic audio stages went fine, but things went downhill in the Balanced modulator. It won't balance. Turning the carrier null pot does nothing, yet I still see signal out. So not sure WTF. But, a carrier out means atleast there is a signal there.

    Routing my way through all the mixers and filters and IF cans, I finally get to the Driver and notice I have NO GAIN in the driver stage! Same output for the same input.

    SO I am going upstairs to look for another 12BY7A

    On a positive point, I replaced the Power Plug with a good shielded Home Depot plug and put feet on the heavy PS. Also got the Power input receptacle all cleaned up so now there is no intermittency. Bit by bit it is closer to working.

    Not sure WTF with the Balanced modulator. Maybe one of the diodes is blown.
     
  8. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    Man, that was a HARD afternoon over the O-scope trying to figure out what is what!!!

    No problem with the Driver 12BY7A! If U got no GOES IN, you can't expect a GOES OUT!

    So backtrack to the TX Mixer!

    There is the TX Mixer that adds the SSB Signal with the VFO to make the IF, and then a 2nd Mixer that takes the IF and adds that to the Hetrodyne generator to get the final frequency.

    I see some signal from the Xtal filter going into the 1st TX Mixer, and see the VFO signal fine, but I DON'T get 6 Mhz IF signal out!!! However, the same transformers are used on Receive as TX, so they are OK. They switch in and out tubes between TX and RX. VERY VERY COMPLICATED!

    I finally stopped making progress, so it is time to throw in the towel for today.
    RX works nice but we are a LONG ways from TX. Very very Exhausting! I can't remember when I worked so HARD on a unit. Again, I really need an Example unit to take reference levels from to compare and see what isn't up to snuff. All I can go on is the Schematic, which so far seems to be correct.

    Atleast it is somewhat isolated. It COULD be that I don't have enough signal level from the balanced modulator (which doesn't balance any way) and that is why the mixers aren't mixing. I don't know. My brain is numbed out now and I need to sleep on it for a week or so.

    The guy I got it from had sent it to some "Expert" who gave up and sent it back to him. Now I can see why he gave up. This is REALLY BROKE!!! It might be another "Museum Service" radio!!! But I have alotta money in this to just stack it on the Shelf!
     
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    This is beginning to sound like something basic.
    You have no transmit but you have receive, lets try and reason this out.
    If it is receiving you know most of the same signal path and the same states are working, this is a good thing.
    The next thing I would look for is one of the transmit stages such as the first mixer in the transmit chain.
    Do you get TX audio to the balanced Modulator?
    If you do then move to the first mixing stage in the transmitter, see if you get the transmitted signal there, and I would use something easy to see like speech as the transmit audio source.
    If you don't get this signal or you are not getting transmit audio into the BM, odds are you have a control T/R control signal that is not making its way to turn on the stage or stages in the transmitter.

    I am willing to bet a Mc Donald's lunch in those first two stages you will find the symptom that will lead you to the problem.
     
  10. WA6MHZ

    WA6MHZ Subscriber QRZ Page

    I DO see good audio on the balanced modulator. Same with the Carrier Oscillator, Do see good level of RF. But that is the key! HOW MUCH is a "GOOD LEVEL"???

    I downloaded the SR-400 schematic and was pleased to see it has much of the exact same circuitry. So I am going to put the SR-400 on the test bench (It needs the T/R relay reworked anyway after Field Day) and take alotta level measurements. I have a really good scope with cursors for measurements of levels and frequency of the Waveforms. By taking critical measurements, I can see where the DIFFERENCE is and that will give me a clue to what isn't working on the SR-2K.

    Primarily the difference between the 2 radios is the Power Amp. The 400 uses a pair of 6HF5s while the 2K uses a pair of 8122s. It's essentially the same radio all the way up to the Driver!
     
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