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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Tue 29, 2018 8:27 pm 
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For a common outputs like 25/50L6 far too much is made of matching specs, as long as one isn't totally dead you'll probably never know difference.. With 150v B+, will deliver 3-4x times the listenable audio you'll be able to use..

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Wed 30, 2018 3:37 am 
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35Z5 wrote:
For a common outputs like 25/50L6 far too much is made of matching specs, as long as one isn't totally dead you'll probably never know difference.. With 150v B+, will deliver 3-4x times the listenable audio you'll be able to use..
Good point, Tom. I wasn't too serious about matching for that reason, strictly a Lo-Fi project here. I picked the two that looked best side by side. :lol:

I did a cap change marathon and ran a test, still with the 25L6 tubes. There is less snap crackle pop, sounding better. I patched the tweeter into the speaker socket with the 6". Tweeter sounds a little too harsh and is pretty quiet compared to the stock speaker. The crossover is a 3 ohm R and a 4 mfd cap. Probably won't be using it.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Wed 30, 2018 12:33 pm 
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Suggest installing a choke in series with the woofer.

The choke has to be selected to provide the correct roloff at the crossover frequency.

Without the choke the 6" is reproducing as high as it can go and may overlap into the tweeter's range which could explain the harshness and mismatched tweeter level given there is a frequency range that is being reproduced by both the 6" and tweeter which makes that range of frequencies sound louder.


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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: May Wed 30, 2018 8:11 pm 
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Thanks, I'll look into that maybe if I get the urge for more treble. This speaker does a good job actually. With the handy speaker socket, I could try a bookshelf speaker already set up with crossover network.

I have the 50L6's running in place of the 25L6's. I found that one of my razor outlet transformers put out 130 vac, so reversed puts out 105 vac. With the load of the power tubes only, voltage dropped to 94 volts. then with B+ spliced in, voltage drops to 91 vac at the secondary of the transformer. I'm once again looking for small transformers to sit on the chassis, but heat again is an issue. 20 volt/amps should be ok, but over the course of a few hours, heat gradually builds up.

Edit: Nope, after about an hour, I shut it down, razor transformer getting hot. Tried the mid-sized piggy-backed transformers and again, one of them heats up. Subbed in a different one, same grief.

I have a large transformer that will power this radio no problem, but it is way oversized, about 4" square, wider than the chassis which is 3 1/2 " wide. Also it weighs too much to be slung under there on 2 chassis screws, won't work. It could go below the bench with an umbilical cord to the radio but that's not smart nor elegant.

The pair of 50L6 tubes with one or two 12 volt tubes will run on house power, so it is an improvement that needs no large dropping resistance. A 6 volt transformer will supply the remaining 300 milliamp tubes and the pilot light.
I'll keep my eyes peeled for a hefty 100 - 120 volt transformer.

I'll put the 130 vac isolation transformer to supply B+. Then with B+ isolated, I don't need to mess around with the switch wiring.
The 112 vac loop for the power tubes and V1 will be floating. I don't think that circuit needs a cap to the chassis.
I chose the 12SA7 for my front end replacement because I have a mess of them, and so do a million Bakelite radios from 1939 to about 1950. It needs to be a 0.15 amp tube to be in series with the 50L6's.

A toggle switch will turn power on to the heaters, and the radio switch will energize B+, a standby switch arrangement that I like. Before I turn on the power, I check that B+ is off.

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Last edited by westcoastjohn on Jun Mon 11, 2018 5:29 pm, edited 1 time in total.

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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: Jun Thu 07, 2018 6:27 pm 
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Best results so far - The Razor outlet transformer is supplying B+ only, with a 47 ohm resistor to reduce the 130 vac output. The B+ is 124 vdc. With the resistor bypassed, 136 vdc, but with no discernible change in volume or audio quality. So I am keeping it conservative at 124 vdc.

On 118 vac filament volts, two 50L6 power tubes + 12SA7 in the front end + 11 ohm 5 Watt R. With one Canadian 50L6 paired with the US tube marked Admiral, the Admiral draws 56 volts on the filament to the Canadian 45 vac. Swapping in the other US made 50L6 that appears to have similar construction to the Admiral, voltage is more even, 50 to 52 vac each. With 11 ohm resistor in the string, there is 11.5 vac on the 12SA7 after warmup.

The larger transformer has a 6.3 v secondary for the two remaining 300 milliamp tubes and the pilot light.

I won't try to squeeze my new power supply onto the chassis right away. But .. maybe possible, with the power tubes moved over.... ?
The 20 volt/amp razor iso trans is getting warm over the course of 3 hours, so I've decided to connect two of them with primaries and secondaries in series, so they are like a center-tapped transformer not using the center taps. With double the iron and windings, there will be less heat, hopefully.

Probably I should order up 150 milliamp tubes 12SF7 and 12SC7. Then I could use a smaller 12 volt filament transformer, and everything will run cooler.

Conclusion:
Will run this setup on the bench for a couple of weeks while I work on the cabinet and other gems. Overall, I'm happy with it. Audio is better than the typical AA5.


Attachments:
Diagram.jpg
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NewPS.jpg
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 Post subject: Re: Westinghouse H-122 conversion
PostPosted: Jun Sat 09, 2018 1:43 am 
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Update: Now have 3 transformers in total.
The small iso transformer from a razor outlet, 20 volt/amps, gets too warm after 4 hours of supplying B+ of about 120 vdc.
So I've connected another to it in series. This is better, less heat buildup so far.

Attachment:
Circuit Lab Trans.png
Circuit Lab Trans.png [ 24.81 KiB | Viewed 1206 times ]
I am using the third configuration here, XFRMR's 5 and 6.

Does this increase the volt/amps rating? It is certainly handling the current better, as there is much less heat being generated.

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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Sat 09, 2018 6:48 pm 
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More than likely there is less heat due to each transformer only having 60Vac on the primary.


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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Sat 09, 2018 7:10 pm 
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Ok, that makes sense.

Calculating the max output with the lower voltage:

120 vac @ 20 VA = 0.16667 amps,
60 vac @ 20 VA = 0.3333 amps.

By the math, 20 VA ought to be just sufficient for the 0.15 amp tube string, but at max output, the transformer gets too hot. So transformers in series is an option. I will look for a couple more of these razor outlets at the surplus building supply place.

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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Sun 10, 2018 4:38 pm 
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Paralleling primary & secondary will double the VA ratings. Just have to be sure windings are in phase(otherwise magic smoke escapes).

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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Mon 11, 2018 12:10 am 
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35Z5 wrote:
Paralleling primary & secondary will double the VA ratings. Just have to be sure windings are in phase(otherwise magic smoke escapes).
I got lucky and we passed the smoke test. But appreciate the warning.

How can one be sure phase is correct? I wasn't sure, so used the orientation of the leads, similar construction from the same manufacturer, and also crossed my pinkies.

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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Mon 11, 2018 2:31 am 
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To check for phase wire the primaries in parallel then connect one end of each secondary together and measure the voltage between the the two wires that are left.

If windings are in phase you should see 0Vac. If windings are out of phase you will see double the AC voltage.


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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Mon 11, 2018 4:57 am 
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OK, I wrote that down and drew a diagram. 8)

Had the radio on all day with normal temperatures on the transformers, success!

The standard glue for Bakelite is super glue. What I have here is Weldbond, a super strong white glue that dries clear. It is recommended for gluing glass and plastic as well as wood, so I thought why not Bakelite? It worked great. I like the fact that it is easy to work with, slow drying, and can be mixed with Bakelite dust.
I think I will still put some epoxy and a bit of cloth to the inside for a permanent repair, but just the Weldbond seems plenty strong, and the crack is tight.

Update: I have my plan for the transformer cabinet. The Westinghouse Rat Rod gets a belly pan from a Heathkit stereo tuner. It is crazy but I don't even need to drill holes to attach it to the chassis.

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 Post subject: Re: Westinghouse H122 power transformers in series question.
PostPosted: Jun Sat 16, 2018 6:59 pm 
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A dismantled Heathkit stereo amp from about 30 years ago was saved in my junk boxes. One of the cabinet panels makes a perfect belly pan for the Westinghouse. I've finished off the under chassis wiring and made sure nothing can short to the new pan.
I will need sides and top for the power supply, and a power switch mounted on a bracket or panel back there.
But I can see clearly now .... all of the bad feelings have disappeared... the complete package will come together soon. 8)


Attachments:
Chassis1.jpg
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Chassis2.jpg
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Chassis3.jpg
Chassis3.jpg [ 154.77 KiB | Viewed 1109 times ]

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 Post subject: Re: Westinghouse H122 has new power supply.
PostPosted: Jul Sat 28, 2018 5:38 am 
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Performance is good, no major issues.
I've started the cabinet over the power supply, a maple plank that needs to be stained similar to the original phono unit. But ..... while the power supply is keeping its cool, relatively, two 50L6 tubes generate a lot of Heat.
Directly above the tubes, the Bakelite gets up to 140 degrees F. :x

I should get more air circulating in there. The US versions of this radio have large rectangular openings in the back, while this one has the usual small holes grill. The original tubes were 25 volts, but there were 3 of them with the rectifier, and the back is warped from the heat.

A better, cooler, cab design is called for. The radio on top of a 10" speaker with the transformers in the speaker cabinet below. With legs, it will start to look more like the VEF Super Luxus. :lol:


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DSCN5752.JPG
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DSCN5759.JPG
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VefSuperLuxus.jpg
VefSuperLuxus.jpg [ 50.23 KiB | Viewed 923 times ]

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 Post subject: Re: Westinghouse H122 has new power supply.
PostPosted: Jul Mon 30, 2018 11:47 am 
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Yes put it on a 10" speaker then make a push pull 50L6 or 35L6 amp with a 12SL7 as the driver which could replace the original amp or be a stand alone amp.


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 Post subject: Re: Westinghouse H122 has new power supply.
PostPosted: Aug Thu 09, 2018 9:19 pm 
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A stand alone amp >>> a powered stereo speaker. 8)
Could use a pair of speaker cabinets, one with the Westinghouse attached.
If I wasn't half deaf in one ear it would be worthwhile. :lol:

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 Post subject: Re: Westinghouse H122 has new power supply.
PostPosted: May Fri 03, 2019 8:29 pm 
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About 8 months later, I can say that I am quite pleased with this radio, which is set to receive the CBC on AM or the local FM stations on the Panasonic Discman when I switch to phono. A second FM receiver gives me 3 stations on rotation as they go to commercials or uninteresting talk.

The 50L6 tubes are not creating as much heat as feared earlier. The wood part of the cabinet never got built but the parts are there.
The heart of this project is the center-tapped output transformer. Pictured here before the recap. If anyone has a Westinghouse H-122 or 155 chassis, shoot me a PM. 8)


Attachments:
WestOT.jpg
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Wes50s.jpg
Wes50s.jpg [ 87.72 KiB | Viewed 149 times ]

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