Hi does anyone have any info on a Kriesler 280 it's a 10 valve Dual Wave console from 1936
I have had the set for some time and got it working again but it isn't working correctly it uses a push pull 6F6 output system.
I have replaced all the capacitors and resistors that needed replacement but it has been modified around the 6F5 and 6Q7 which has been changed to a 6G8G but not correctly.

I can see after servicing it and doing checks the cathode of the 6F5 is positive 65V! what someone has done is after the cathode bypass eletro and resistor a 2500 ohm they have added a 100k resistor to earth, a 01 mica to the grid of the 2nd 6F6 and a 250k resistor from the negative of the eletro to the grid of the 6F5 then again through a 01 mica to the plate of the 6G8G.

Its original line up was:
5Y3G
6F6
6F6
6F5
6Q7
6E5
6K7
6K7
6A8
6K7

https://www.radiomuseum.org/r/Kriesler_280.html

I have also included the link to my console on radio museum, any help is much appreciated
Stephen

Those numbers minus the "G" are likely metal types. Most of the metal types (not all) have pin one (or the body pin) grounded. If that pin has been used as "a pin of convenience", for something else, all hell can break loose.

This looks rather like its been well & truly hacked. It is difficult without a circuit to ascertain what has been done. 6F5 was used a s a resistance coupled amp. Plate resistor 0.5Meg, grid leak 1Meg, cathode 5400 ohm. It all sounds a bit odd, but the grid voltage should be checked -2V is recommended for the grid but that is relative to cathode.

If that is push pull? that could be the phase splitter? In that era I would half expect a transformer as a phase splitter.

It may be a reverse engineer job, to get a circuit irrespective of any errors. We really do need more info.

Marc

Stephen has probably omitted the Gs. The unit in the photo has glass valves. Stuart Irwin uploaded the photos of the unit shown on Radio Museum. Perhaps he has a circuit diagram. Just pray he sees this thread and can confirm either way - he is a member of this site.

Stuart is in the middle of moving house, I've sent him the details, asking if he could view and respond.

Hi Stephen.

Unfortunately, I don't have any further information on that radio. Certainly not the circuit. In fact, Kriesler does not seem to have any of its circuits reproduced in any trade publications before 1937, although factory service manuals probably exist, - somewhere. I'm certain that metal valves were originally used, as Kriesler made a bit of a feature of this in their more up-market radios. In fact they boasted that their model 9MT of the previous year was the first Australian set to use all metal valves, apart from the 6E5 tuning indicator. Also, I got the valve line up from a list of Australian radios for 1936 published in the 1936 Radio Trade Annual of Australia, and this indicates that metal valves were used. Other Kriesler radios in that list that use octal glass valves, are so indicated with the "G" suffix.

It is interesting that metal valves were quite an advertising and marketing feature in Australia from late 1935 into 1936, but after that many manufacturers reverted back to pre-octal or started using glass octal.

If the 6F5 is used as the phase inverter, as seems likely, then it is quite normal for there to be a load resistor in the cathode circuit. This provides a signal that is 180 degrees out of phase with the signal at the anode. The push pull 6F6s require these signals at their grids.

Hope that helps.

Cheers.

Hey guys thanks for the reply's the photos on radio museum are of my console after I restored it I uploaded them.
It did originally have a all metal tube line up when it first left the factory, but over time these have slowly been replaced. I received it in original condition where it had all 30's papers and a few 40's eletros and a couple of more recent resistors so it was reasonably untouched. I went though the set as it wasn't working and replaced all the caps and resistors like for like, the set works loud and clear but its been modified for sure on the 6Q7 which was replaced with a 6G8G and the other issue it has is the magic eye isn't getting enough negative volts to close on a station it only gives -0.5 on its grid which could be related to the 6Q7 swap.

But without a schematic I cant prove that the rest hasn't been slightly altered over the time either
It still has 3 metal tubes a 6K7 6A8 and the 6F5 the rest of the tubes are all NOS that I installed and will swap them back to metal as I acquire more valves.

Unless we can track down a schematic the only option I have is to draw out whats there and then we can review the circuit

Hi Stephen. I'd say there is something definitely wrong if there is no AGC voltage for the eye. A set like that will be highly sensitive and I would expect 20 to 30 volts negative to be generated when tuned to a local station. Too many possible causes to list that could cause poor sensitivity.