HMV 1124 - Has Been Tested And........

[Murphyv310]

Hi.
Let's dispel some myths. Smoothing cans can contain one or more separate capacitors. They will not be internally connected together with either a resistor or by direct connection.
A multi capacitor ( more than one section) by default will be marked thus. Black=chassis, negative. Red=reservoir usually directly connected to the rectifier cathode. Yellow=smoothing capacitor fed from the reservoir via either a choke or high wattage resistor, both reservoir and smoother are at positive HT potential.
Other colours on a multican smoothing block (green, blue etc) are for other sections. Sometimes instead of black no marking can mean chassis, negative.
Being honest all this is very basic, from what I've read in your many posts is you are not really grasping the fundamentals. The books you have should help but I really think you need someone to mentor you on a one to one basis.
Without  being cheeky how on earth can you think of fixing radios for commercial gain when you don't seem able to grasp a simple power supply? 

As an aside motor run caps are NOT designed for smoothing applications.

[AlanBeckett]

Motor run caps are NOT designed for smoothing applications.

Although they will work OK. On the other hand Motor Start Capacitors are not suitable as they're designed to take a huge surge for a very short time.

On some Can Electrolytics there isn't a specific Negative Connection, just the Can which is clamped down to the Chassis.

Alan

[Murphyv310]

Motor run caps are NOT designed for smoothing applications.

Although they will work OK. On the other hand Motor Start Capacitors are not suitable as they're designed to take a huge surge for a very short time.

On some Can Electrolytics there isn't a specific Negative Connection, just the Can which is clamped down to the Chassis.

Alan

Hi Alan.
Let's not get pedantic, would you fit a motor run cap as a smoother? I wouldn't,  it's not the correct component, it's doing a job it wasn't intended for.
When I was fixing industrial equipment, some motor run caps say AC only, Nowhere Man is confused enough so let's get him used to using the correct components don't you agree?

[AlanBeckett]

Yes, mostly. I wouldn't fit one either unless I was desperate to get something going.
Actually, High Voltage Electrolytics are more readily available these days then were in the past so there's no reason not to use something within striking distance of the original.

Alan

[pwdrive]

Don't forget that some of the old electrolytic cans contained the HT capacitors and sometimes the audio output cathode bypass capacitor, it pays not to get the connections wrong on those.

Lawrence.

[Nowhere-Man]

Don't forget that some of the old electrolytic cans contained the HT capacitors and sometimes the audio output cathode bypass capacitor, it pays not to get the connections wrong on those.

Lawrence.

You can see in the pic attached a German rectifier and smoothing circuit in a vintage German tube radio. The layout and design of the set is very different from vintage British sets. One other factor is it's a transitional set from mid sixties so part of the radio actually uses printed circuit board, including the tube pins of the other tubes soldered to PCB. I can't recall what the rectifier tube was on the German set.

When the idea of silicon rectifiers first came out in the early sixties, the fact was a lot of rectifier tubes were being discarded by HAM enthusiasts and silicon was considered a better alternative. I recently read some interesting comparisons between silicon rectifiers and tube rectifiers and am becoming inclined more towards silicon. Suffice it to say I got great results using semiconductor diodes with a resistor capacitor network.

On the HMV the rectifier is a standard U10.

I did make a few more tests with the U10 last night, especially the transformer leads. It kicks out close to 390 volts DC Ripple which is pretty high although the manual data states the workshop test result was about 380.

Objections were raised by some other posters about my testing the H.T. smoothing can on the HMV. This simply involved charging the 16 mF capacitor and then also testing how long it took for the charge to dissipate across a lamp. I've found differences in these tests between different sets and was curious.

I was likewise curious over the rectifier wiring on the HMV and it seems I may well modify this to see if I can improve on the original layout. I did like the use of 2 one amp fuses in the mains supply on the rectifier mounting platform but some things about the rectifier layout I don't like as it stands.

As for the German set, nothing beats German engineering at that time.

[Nowhere-Man]

Motor run caps are NOT designed for smoothing applications.

Although they will work OK. On the other hand Motor Start Capacitors are not suitable as they're designed to take a huge surge for a very short time.

On some Can Electrolytics there isn't a specific Negative Connection, just the Can which is clamped down to the Chassis.

Alan

Hi Alan.
Let's not get pedantic, would you fit a motor run cap as a smoother? I wouldn't,  it's not the correct component, it's doing a job it wasn't intended for.
When I was fixing industrial equipment, some motor run caps say AC only, Nowhere Man is confused enough so let's get him used to using the correct components don't you agree?

I think you're confusing "confusion" with "curiosity".

On another large vintage radio website, in the past,I couldn't help there were people who had blown tubes (by rushing ahead?) and were forced to search EBay for substitutes which weren't always so easy to get. Personally I'd rather get it right first time even if that means going over seemingly straightforward circuitry and testing repeatedly. Given one of the tubes is an X78 Triode Hexode which retails at around £30.00, I'm treading carefully.

I haven't personally used the motor caps but I do know people who claim to have successfully used them. They're available at 440 volts 16 mF on the shelf but it's not the starter caps that were used. I can't comment more on that as I haven't used them myself.

[Nowhere-Man]

I couldn't help but get this feeling of "quasi prehistoric" looking at that U10 rectifier. When you think a couple of tiny diodes, a couple of capacitors and a resistor does the same thing. Also, the fact you can use capacitors to reduce the amplitude of the output voltage. For example, using just the silicon diodes the D.C. output ought to be 1.414 the A.C. (about 360 D.C.)However, with capacitors used in a capacitive reactance circuit, this can be compensated.

Only bone of contention has been the delay between cathode/anode load and a surging initial output voltage. This didn't seem to bother the amateur radio builders who viewed silicon as a Godsend.

I did hear of reverse wave tube rectifiers used in some battery sets. These actually rectified the negative waveform at the cathode and supplied a D.V set supply voltage at the anode.

[Crackle]

I couldn't help but get this feeling of "quasi prehistoric" looking at that U10 rectifier. When you think a couple of tiny diodes, a couple of capacitors and a resistor does the same thing. Also, the fact you can use capacitors to reduce the amplitude of the output voltage. For example, using just the silicon diodes the D.C. output ought to be 1.414 the A.C. (about 360 D.C.)However, with capacitors used in a capacitive reactance circuit, this can be compensated.

Only bone of contention has been the delay between cathode/anode load and a surging initial output voltage. This didn't seem to bother the amateur radio builders who viewed silicon as a Godsend.

I did hear of reverse wave tube rectifiers used in some battery sets. These actually rectified the negative waveform at the cathode and supplied a D.V set supply voltage at the anode.

Hi NM
What has all this got to do with the HMV radio you have on the bench, do you want to get the radio working or not?

Mike

[Murphyv310]

I couldn't help but get this feeling of "quasi prehistoric" looking at that U10 rectifier. When you think a couple of tiny diodes, a couple of capacitors and a resistor does the same thing. Also, the fact you can use capacitors to reduce the amplitude of the output voltage. For example, using just the silicon diodes the D.C. output ought to be 1.414 the A.C. (about 360 D.C.)However, with capacitors used in a capacitive reactance circuit, this can be compensated.

Only bone of contention has been the delay between cathode/anode load and a surging initial output voltage. This didn't seem to bother the amateur radio builders who viewed silicon as a Godsend.

I did hear of reverse wave tube rectifiers used in some battery sets. These actually rectified the negative waveform at the cathode and supplied a D.V set supply voltage at the anode.

Hi NM
What has all this got to do with the HMV radio you have on the bench, do you want to get the radio working or not?

Mike

Mike.
I'm getting confused. 
NM needs mentoring, he has some ideas that are plainly incorrect, the books won't help but possibly one to one help may.