PhilAndrews

'51 Chieftain - Getting back to it

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I've put the radio back on my workbench (first time in over a year) and plan on getting back to the conversion and rebuild.

 

Just had a head-scratching moment but found the power transformers have a fairly significant revision change between the years so I need to re-draw the circuit diagram to account for that.

 

Phil

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Benefits of AACA Membership.

20200514_132040.thumb.jpg.71ac86b4efaa3fc2e137be8746361f80.jpg

There we go. With the exception of the 6 prefix on the tubes (going to replace them with the 12 variants) that's what's getting built. 

 

Phil

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Nope. This is.

 

20200515_152219.thumb.jpg.1645e7424f3fb1ff20bc0a22b0bf0efb.jpg

 

Minor revision, helps if you actually look at the chassis to see what's fitted when there's alternative choices.

 

Phil

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On 2/19/2019 at 6:54 PM, PhilAndrews said:

Is there meant to be a lower bellhousing cover?

 

The manual picture looks like there should be.

 

Phil

yes, pontiac used a sheet metal lower inspection cover to protect the flywheel/torus from the weather.

 

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12 hours ago, PhilAndrews said:

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Getting a collection of parts together, preparation to rebuild.

 

Phil

phil, i have several 53-54 pontiac chieftain parts radios, so if you need a replacement tube for one that's bad, call me 4176935219, charles.

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Posted (edited)
6 hours ago, pontiac1953 said:

phil, i have several 53-54 pontiac chieftain parts radios, so if you need a replacement tube for one that's bad, call me 4176935219, charles.

 

They'd have to be '56 onward- this is going to be (probably) the only 12V '51 radio out there.

(Unless I'm getting my years wrong, when did Pontiac go 12V?)

 

Phil

Edited by PhilAndrews (see edit history)

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Pontiac went 12 volt in 1955. 

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Ok, I thought it was 55 or 56.

 

I've bought the 12V heater variants of the tubes the '51 radio uses. The B+ power supply is now natively 12V.

I didn't want to be running the radio through a voltage dropper circuit. They get a little too hot for my tastes. The radio gets warm enough as it is.

 

Phil

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20200522_110701.thumb.jpg.3e95a290a6badb313933f0e9fab8280a.jpg

14C5 power output tubes arrived.

 

The rest of the bits that I actually need to start are typically first to have been ordered and last to arrive....

 

Phil

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20200523_224106.thumb.jpg.6fb8beb3ed522f2cf852836b10944e34.jpg

Volume and tone control.

 

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Made a fair bit of headway tonight. More tomorrow.

 

Phil

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20200524_111114.thumb.jpg.97239a85766e9395985235093776a5a7.jpg

Component parts complete (apart from one bit which isn't a showstopper).

 

 

Plays okay. Not bad reception for around here.

 

Phil

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Resolved a number of issues with Delco's design that would have resulted in horrible whine and chatter from the alternator and ignition circuits.

 

 

 

Also got the Bluetooth hooked up and working nicely. Might fit a more modern speaker with a mid and a tweeter.

 

Phil

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That's too high tech for this guy! I ended up buying a RediRad to hook up to my IPod to play 50's music that way. I also love the crappy sound the original speaker makes LOL. 

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Posted (edited)
5 hours ago, Summershandy said:

That's too high tech for this guy! I ended up buying a RediRad to hook up to my IPod to play 50's music that way. I also love the crappy sound the original speaker makes LOL. 

 

Barring the 12V conversion (which is done the way Delco would have done it if it were required to have been from the factory) and a few extra filter capacitors to shut it up from external interference on the power input, it's rebuilt to original spec. All I did was hook a Bluetooth doodad into the volume control (and isolated it in case the grid collapses in the tube or arcs out).

 

Real straightforward. This was an enjoyable rebuild compared to the Zenith. All in so far to convert, rebuild and upgrade has set me back about $200. (Bought 2 radios, a full compliment of tubes, resistors and capacitors, plus the Bluetooth board).

 

On AM it's as crackly as ever. On Bluetooth it's genuinely HiFi, the power amplifier is a very good design. Much better than I would expect from an AM set, to be honest. The speaker's response is geared towards 2-4kHz peak, which is where the audio from AM lives- with a full range speaker this has proper 20-15 performance.

 

Props to Sylvania for the design.

 

Just looked at RediRad's website- nice touch. That's a sensible idea though they could do with a Bluetooth option in there too, rather than solely plugin options. Does make it sound authentic though! It's limited not so much by the speaker but the bandwidth of AM radio, which is 8kHz, giving a maximum Nyquist frequency of 4kHz to your ears, about the range you get over the phone. 

I bypassed that and connected in at the point the radio circuit ends and the audio amplifier begins. As with most AM radios, the power amplifier and speaker are capable of significantly better performance than AM can supply, but you never really get to hear that.

 

For this, I didn't have to gut anything (didn't want to, either because as soon as I took a look at the schematic I could see it wasn't a bad design) instead merely rebuild and tweak slightly where required. I added a few pieces they supplied with the radio to be fitted externally because they were quite big. Modern ones fit inside the radio.

 

Phil

Edited by PhilAndrews (see edit history)

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Not bad at all. Editing blip isn't smoke and mirrors, I just cut 6 seconds of awkward silence as my old phone decided to take that particular time to be slow to pair to the Bluetooth.

 

Phil

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20200603_152658.thumb.jpg.6d6502f96535988372d03c096d118910.jpg

Hopefully the last reassemble, made a foam rubber cone like it would originally have had.

 

Phil

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57 minutes ago, PhilAndrews said:

Question, how does the rear seat pull out?

 

Phil

pull the front of the rear seat cushion up and forward, then unfasten the bottom of the rear seat back rest.

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Thought so, it just doesn't want to budge. I didn't want to be forcing something the wrong way.

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Just now, PhilAndrews said:

Thought so, it just doesn't want to budge. I didn't want to be forcing something the wrong way.

you may have to push inward to pull up the cushion

 

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