The following images are of the Super Hetrodyne chassis that came with the radio. As you can see it has been butchered and is being rebuilt.
No valves (tubes) were fitted to any of the sockets and the IF amplifier valve had been replaced with an unknown Octal type. The aerial coil was open circuit and the oscillator coil had been repaired. I have found suitable replacement coils. I have not checked the IF coils yet other than simple continuity check and they seem to be OK. Only time will tell.
I have almost finished putting this chassis back together using a circuit diagram from another set of the same era.
I have a sneaky suspicion the super het should have a reflexed IF stage because as far as I can tell this was the time when Astor was famous for this technology.
Recently, Kevin Chant passed on the following information on this receiver: Checking my data on the Astor it shows the Caliph was produced in 1933 and 1934 with three chassis's available, the H, H80 & PZ. It states that the circuit info is in the Astor book on page 86 ?
I also found in another book reference to a 1934 Caliph with chassis SAG, this was a dual wave console, still with five valves and 456 I.F.
Can you shed any light on these sets and would you have any circuit diagrams for either chassis or perhaps both ?
The super het chassis had been butchered with a couple of very in appropriate octal valves and wiring that was going to destroy whatever was still working.
The next four photos are of my finished restored chassis for the 401A with a 6 Volt vibrator supply fitted. This came from an earlier version of the same radio supplied by Greg Lamey. Thanks Greg.
Written on the chassis in pencil was the following valve types next to three of the octal sockets:
Converter "6J8", First IF "6U7", Second IF "6U7"
It looked to me as though the detector and audio preamp could have been a 6B8 or a 6G8 but there was not enough of the wiring around what I presume was the audio output stages to see what it may have been. There were five valve sockets wired with at least four the heaters in series. The fifth valve socket had the wiring removed. Was it wired with five 300 mA 6.3 Volt valves in series, this adds up to 32 Volt. There is another two octal sockets that look like they were wire in parallel. I have put labels on the valve sockets in the under chassis photo.
Alistair McAlister had a suggestion as to what the two extra octal sockets may do. These look like they were wired in parallel. His suggestion is there was a pair of 35L6 valves in the output, wired in parallel or push-pull.
Talking to Greg Lamey, our HRSA groups local 32 Volt radio expert, he suggested the output stage may have been transformer driven push pull configuration and this fited well with what I could see left of the wiring of this area. The plate pins on the two valves I guess are the output valves have the remains of a blue and a brown plastic covered wire on them, typical of the small push pull transformers Rola built in those days. He also suggested the output may have been 25L6 or 35L6 valves. This means the mystery octal socket would have been the driver stage. It all made sense then. I even found a suitable Push-Pull output transformer on an old junk chassis and the colours of the Anode wires were even the same.
Rummaging on the internet for data on the 35L6 output valve I stumbled on an old Vintage Radio page in Silicon Chip magazine and it was about the Diason P.P.32/6, another 32 Volt DC receiver. This receiver used a conventional triode phase splitter instead of a driver transformer.Have a look at the circuit in the article here.
I de-rusted the chassis and painted it with zinc rich primer. Looks like several generations of Mice hade lived in this receiver, there was a lot of evidence of their bad toilet habbits. I also replaced all the original capactors, pitty about the small size and construction of most of these but it is the only economical way to do it these days and be sure the components will last for many years.
I wired the fifth octal socket for a 6J5 triode used as a phase splitter circuit. This gave me five 6.3 volt valves in series. I then wired the two output tube sockets in parallel for a pair of 35L6's and connected the heater strings to the 32 Volt line.
The broadcast coils were ruined by the mice (they do rule the world) and so I replaced these with the coils I have mentioned elsewere in my web pages.
I found an article about a Monarch D671/32 in the April 2005 Vintage Radio column in Silicon Chip magazine. Looks like this receiver from Astor was also branded National D791/32 because it is exactly the same as my set.
Looking at the circuit in this article I have made a few mistakes, I have used a 6J5 as a Phase Splitter, they used a 6SN7 as a Voltage Amplifier and a Phase splitter. As the 6SN7 had a 0.6 Amp heater they had to wire 20 Ohm 5 Watt resistors accross the heaters of the other four valves. I like my arrangment better. They also used 25L6's in the push pull output and had to put an 11.5 Ohm 20 Watt resistor in series with these tubes. They also had a 100 Ohm 20 Watt resistor in series with the 6.3 Volt 300 mAmp dial light. I am going to cheat and use a white LED. I am sure Rodney Champness would agree with my changes.
I found service information for both tese receivers on UK Vintage Radio Service Data A great resource if you are after service data for radio receivers built in the UK.
I have had this BIG old valve amplifier for more than fourty years. It was one of a handfull of tuner-amps made to receive the short lived experiment with AM stereo where each channel was broadcast on a separate station. Read about the second restoration project and see more photos here. I have included a link to a paper on the history of FM broadcasting DownUnder. Was Australia the only place where the idea of using two AM stations for stereo was tried ?.
The markings on the chassis are:
The ARTS&P has a G prefix, 1940 I presume
Stamped into the chassis is K3967
Printed on the chassis is 1640