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Dangerous Newbie With a Philco K-1721
Dangerous Newbie With a Philco K-1721
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Old 15th April 2018, 01:05 AM   #1
metsno1 is offline metsno1  United States
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Default Dangerous Newbie With a Philco K-1721

Hey All...

After hoping for many years to run into a tube amp that I could afford at an estate sale or Goodwill, I finally ran into one a few days ago and I couldn't resist.

It's a *gorgeous* Philco K-1721 console from 1962 that had been in the exact same location since new. It's in near pristine cosmetic condition, the turntable is perfect, and when I turned her on, everything worked 100%. Sounded absolutely amazing. So I plunked down my $100 and brought it home and all was well. Connected a CD player through the "tape" input and carefully vacuumed out the interior. *Very* odd design, with only a single 12" woofer mounted below the left side mid and tweeter. Right side has only a mid and tweeter. But again, the sound was borderline phenomenal. It competes well with my current Sansui Quad receiver/Klipsch Heresy setup, and in some ways exceeds it.

Anyway, I let it run on FM for a few hours and started to notice some crackle in the left channel that hadn't originally been there. And then the left channel cut out. Let it sit for a while and turned it back on. Left channel was fine for about ten minutes, then scratchy, then cut out.

So I went in and swapped the right and left tubes. Turned it on and all was well. But then after about ten minutes, same crackle on the left (with the tubes switched). Turned it off. Turned it back on again, and the left channel was out.

I let her sit for several hours, and then went ahead and pulled all the tubes, cleaned the pins with deoxit, cleaned what I could comfortably reach with the deoxit without going crazy and let her sit overnight. No change in status the next morning. Still crackle in the left channel, and eventually it cuts out.

I am a *total* newbie when it comes to anything more than cleaning contacts and maybe doing an odd recap here and there. I've been reading about issues with resistors causing this type of behavior, but I literally don't even know how to identify a resistor visually.

So I need some help on where to start to learn what to do to get the left channel back up and running properly. I'm not afraid to really take my time to understand that what and how of whatever needs to be done, and any help would be appreciated. She's way too gorgeous to not have working in peak condition!

Thanks so much!
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Old 15th April 2018, 01:47 AM   #2
mkane77g is offline mkane77g  United States
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Dangerous Newbie With a Philco K-1721
Just keep one hand in your pocket while poking around and rubber-soled shoes are not a bad idea. Take a resistor and wire up a pair of alligator clips so you can discharge the caps. Discharging capacitors
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Old 15th April 2018, 01:57 AM   #3
PRR is offline PRR  United States
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Quote:
Originally Posted by metsno1 View Post
...I literally don't even know how to identify a resistor visually....
Turn it over to an experienced person, or spend much time in Google, starting with image-search.

Yes, some of these were very-very pleasant music players. This one put all the money for two channels of bass into ONE better bass amp and woofer. It is perhaps "too clever", but such schemes sometimes work better than expected.
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Old 15th April 2018, 02:02 AM   #4
kevinkr is offline kevinkr  United States
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Dangerous Newbie With a Philco K-1721
A fifty six year console is going to need some TLC, the power supply capacitors should all be replaced, coupling capacitors in most cases too. Check resistors for value change (not always easy due to circuit design) sometimes you can compare one channel against the other. Avoid messing around with the tuner except to replace paper caps and electrolytics. (Do not mess with any of the coils or IF transformers)

Most likely based on your diagnostic approach and the fact that you plugged it right in I'd recommend finding someone experienced with tube gear to help you out. (Maybe someone right here on diyAudio)
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Old 15th April 2018, 02:04 AM   #5
Refugee1 is offline Refugee1  United Kingdom
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I would replace the G1 coupling capacitors on the output tubes before doing anything else.
They are likely to burn out the transformers if you leave them.
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Old 15th April 2018, 02:07 AM   #6
rayma is offline rayma  United States
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Quote:
Originally Posted by metsno1 View Post
I need some help on where to start to learn what to do to get the left channel
back up and running properly.
It could be a bad connection or part, but find someone local to help you.
An experienced person could find the problem easily, and it is dangerous
to work on these. There should be a schematic below the speakers on one side.
Post a photo of it here.

Last edited by rayma; 15th April 2018 at 02:29 AM.
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Old 15th April 2018, 04:08 AM   #7
metsno1 is offline metsno1  United States
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Just a couple of clarifications. The original owner has been using this amp regularly since new. Many of the tubes are not original, and it was already plugged in and playing at the estate sale when I arrived. I just checked out the cosmetic condition, saw the tubes glowing, turned it off and paid my money.

So yes, I'm leaning heavily toward finding someone locally that can work on this for me. I'm willing to spend some money on it, but I'm wondering what constitutes "too much." Does anyone have any idea of an approximate value of this unit in good working order?
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Old 15th April 2018, 12:10 PM   #8
pcan is offline pcan  Italy
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Dangerous Newbie With a Philco K-1721
It seems to be a better than average console, with 7591A single ended output tubes. Could you please take a high resolution picture of the schematics and post it here? It should be glued inside the right channel speaker cabinet. Collector value is low today, but I believe is bound to rise due to the increasing appeal of this early '60 furniture style.
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