29-12-2017, 10:46 AM
Hi.
I have a Seawave DF22 Battery valve set. It is a DF receiver and it works particularly well. The Valve line up is a bit odd but it is the way I got it 13 years ago.
It is DF96.... RF Amp, DK91.... Frequency changer, DF96... IF Amp, DAF96.... Detector/AF amp, DL92.... AF output, DF96... BFO.
It has three bands LW, MW to 2.0mHz SW from 2.0mHz to 6mHz (faulty due to OC oscillator coil)
The DF is a rotatable ferrite rod on the top of the metal casing.
Ever since I have had it has been sore on HT batteries, I replaced all the old caps and all 7 resistors many moons ago, four 2.2m resistors are in the AGC so only three resistors are in the main circuit (1m & 4.7m in the DAF pentode section & 1, 82k in the DK).
It needed a new set of 10 PP3's this week and on switching on the 101v across the 10 PP3's dropped to 80. A quick check on the HT current revealed 27ma. This is far too high for a set of this type so I set about tracing the fault. Firstly removing all the valves resulted in zero current so that ruled out any HT leakage, I then fitted the DF96 in the RF stage and it was drawing a whopping 10ma, a new DF96 dropped this to 2ma still perhaps a little high but obviously the old valve was U/S. The DK & DF in the IF both were drawing around the 2ma mark but the DL output 11ma, The DAF was below 1ma. So we now are pulling 17-18ma with all valves present with the BFO off. I still think this is a little too high.
What I have noticed all screens (G2) bar the DAF are directly connected to HT with no limiting resistors. So far I have added a 4.7K to the DL's G2 with a decoupling cap for a slight drop in total current with no drop in output so I'm considering adding screen feed resistors to the RF, Mixer and IF stages with suitable decoupling. With anode volts of 90 it is recommended that the screens are run at 67.5v, I really cannot imagine that any manufacturer would penny pinch so much and leave out vital components. We will see if the performance suffers after doing the additions.
What is the consensus from others.
I have a Seawave DF22 Battery valve set. It is a DF receiver and it works particularly well. The Valve line up is a bit odd but it is the way I got it 13 years ago.
It is DF96.... RF Amp, DK91.... Frequency changer, DF96... IF Amp, DAF96.... Detector/AF amp, DL92.... AF output, DF96... BFO.
It has three bands LW, MW to 2.0mHz SW from 2.0mHz to 6mHz (faulty due to OC oscillator coil)
The DF is a rotatable ferrite rod on the top of the metal casing.
Ever since I have had it has been sore on HT batteries, I replaced all the old caps and all 7 resistors many moons ago, four 2.2m resistors are in the AGC so only three resistors are in the main circuit (1m & 4.7m in the DAF pentode section & 1, 82k in the DK).
It needed a new set of 10 PP3's this week and on switching on the 101v across the 10 PP3's dropped to 80. A quick check on the HT current revealed 27ma. This is far too high for a set of this type so I set about tracing the fault. Firstly removing all the valves resulted in zero current so that ruled out any HT leakage, I then fitted the DF96 in the RF stage and it was drawing a whopping 10ma, a new DF96 dropped this to 2ma still perhaps a little high but obviously the old valve was U/S. The DK & DF in the IF both were drawing around the 2ma mark but the DL output 11ma, The DAF was below 1ma. So we now are pulling 17-18ma with all valves present with the BFO off. I still think this is a little too high.
What I have noticed all screens (G2) bar the DAF are directly connected to HT with no limiting resistors. So far I have added a 4.7K to the DL's G2 with a decoupling cap for a slight drop in total current with no drop in output so I'm considering adding screen feed resistors to the RF, Mixer and IF stages with suitable decoupling. With anode volts of 90 it is recommended that the screens are run at 67.5v, I really cannot imagine that any manufacturer would penny pinch so much and leave out vital components. We will see if the performance suffers after doing the additions.
What is the consensus from others.
Cheers.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.
Trevor
MM0KJJ. Member of, RSGB, GQRP, WACRAL, K&LARC.