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Colin Walls
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what is that?
Colin Walls   5/23/2014 4:50:41 PM
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Hi Max

First off, diagnosing vacuum tube [sorry "valve"!] falures is not too hard. It is the filament that gives out. If it doesn't glow and get hot, it's dead.  Unfortunately, some designed wire all the filaments in series, so, when one dies, they all appear dead. So you ned to pull each  one and check its filament.  A bit like Christmas tree lights ..

Is that an ASR33 Teletype outside your office? If so, why??

 

BR c

Proclivis
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Re: what is that?
Proclivis   5/26/2014 11:49:14 AM
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I love my old Magnavox. Tubes have such a nice sound when playing an old Chuck Mangioni album. However, I must admit that I rigged it so that I can feed in Air Play from my Mac via my wireless network. The kids really get a kick out of playing Jazz from their iPhone on an old Tube amp. My daugher in music school is hooked on the sound.

Max The Magnificent
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Re: what is that?
Max The Magnificent   5/27/2014 9:13:47 AM
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@Proclivis: I rigged it so that I can feed in Air Play from my Mac via my wireless network. The kids really get a kick out of playing Jazz from their iPhone on an old Tube amp.

Very cool -- I have some 1929 Bakelite headphones that I swapped out the old insides for modern equivalents -- they actually sound amazing when plugged into my iPad.

Max The Magnificent
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Re: what is that?
Max The Magnificent   5/27/2014 9:06:36 AM
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@Colin: If it doesn't glow and get hot, it's dead.

That was always my first-pass way of diagnosing a fault :-)

Max The Magnificent
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Re: what is that?
Max The Magnificent   5/27/2014 9:07:51 AM
@Colin: Is that an ASR33 Teletype outside your office?

Yes

            If so, why??

Because there isn't room for it inside my office :-)

zeeglen
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Don't Fire it up yet
zeeglen   5/23/2014 5:23:30 PM
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@Max:  You would be wise to replace all the paper and electrolytic capacitors BEFORE applying power.  You don't want to fry a hard-to-obtain vacuum tube.  And there is a lot more that goes wrong with tubes than just their heaters/filaments. 

That Grundig radio probably has a power transformer so the heaters will be in parallel, unlike the series connected heaters in the "All American 5".

There is a Yahoo group called "Fun with tubes" that have a lot of good information on restoring antique radios and designing guitar amplifiers.

When I was a little kid my parents had a Grundig radio that looked very similar.

Max The Magnificent
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Re: Don't Fire it up yet
Max The Magnificent   5/27/2014 9:09:39 AM
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@zeeglen: You would be wise to replace all the paper and electrolytic capacitors BEFORE applying power

Sage advice, old friend.

zeeglen
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Does your Grundig radio have a graphic equalizer?
zeeglen   5/27/2014 10:28:47 AM
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I seem to recall the similar Grunding of my parents back in the mid 50's had a row of 5-6 knobs at bottom center which controlled various audio frequency bands.  The visual indications were small beads tied together with red elastic strips behind the glass panel.  As the knobs were adjusted the beads moved up or down about 1-2 cm, the elastics stretched and followed to form a mechanical visual display of the resulting frequency resonse.

 

Max The Magnificent
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Re: Does your Grundig radio have a graphic equalizer?
Max The Magnificent   5/27/2014 10:31:16 AM
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@zeeglen: I seem to recall the similar Grunding of my parents back in the mid 50's had a row of 5-6 knobs at bottom center which controlled various audio frequency bands.

Yup -- this one has exactly the same thing -- I can't wait to get this little beauty up and running...

perl_geek
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Anachronism
perl_geek   5/23/2014 7:12:32 PM
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I think you'll find that the radio dates from the mid 1950s, not the early 1940s.

Apart from the aesthetics, the firm's history http://www.grundig.de/en/company/about-grundig/grundig-history/years-1945-1954/ indicates it was strictly a post-war manufacturer.

If you're going to fix it, you might want to RTFM; http://www.grundig.owner-manuals.com/5088-service-manual-GRUNDIG.html  (I assume the site is kosher, but caveat emptor).

Other people have also repaired them, and the comments suggest it's worth doing: http://www.radiomuseum.org/r/grundig_konzertgeraet_5088_1.html 

 

 

 

vandamme0
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Re: Caps
vandamme0   5/26/2014 11:58:23 AM
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If you feel brave, you can put it on a variable autotransformer and slowly crank it up. Once the rectifier tube lights up enough to work (maybe 25%) you might be able to reform the caps by letting it cook for a few hours, gradually upping the voltage. No guarantee.

If you don't have an autotransformer, try putting an incandescent light bulb in series with it. Try a 25 watt to start.

Your caps might work fine, might blow up, or (most probably) just won't filter well and it will hum badly. Time to get out the scope (check the voltage rating on the probe!) and see what caps have a lot of ripple on them. Also check casthode bypass caps. They can short, or have high ripple.

If you give up, don't throw out the case. Put an mp3 player or internet radio in it.

zeeglen
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Re: Caps
zeeglen   5/26/2014 4:13:30 PM
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you might be able to reform the caps by letting it cook for a few hours

NO! 

This might work for electrolytic caps, but an interstage paper coupling cap that has absorbed moisture will leak and drive a following stage control grid positive, resulting in excessive current and possible damage.


Douglas442
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Re: Caps
Douglas442   5/26/2014 11:52:30 PM
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Max said: "...a vacuum tube radio from the early 1940s. Amazingly enough, I have the perfect spot for it. The photo below shows the bay outside my office. The comfy chair and ottoman in the foreground allow one to take a few minutes' break now and then."



No! Not the Comfy Chair!

 

...anyway, as the proud owner of a whole pile of vintage hp and tektronix equipment, I can only echo the cautionary sentiments of the previous posters.

 

You don't want to take the chance of losing this opportunity. Think of all that you'll be missing, should it become permanently inoperable!... as the store-owner from this classic Charles Rodrigues cartoon ( from the "Over & Out" series in the long-defunct "Electronics Illustrated" magazine, this one from January 1970! ) may have been trying to suggest:

Vintage Radio Cartoon by Charles Rodrigues

Max The Magnificent
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Re: Caps
Max The Magnificent   5/27/2014 9:19:10 AM
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@Douglas: No! Not the Comfy Chair!

Nobody expected the...

Max The Magnificent
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Re: Caps
Max The Magnificent   5/27/2014 9:15:41 AM
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@vandamme0: If you feel brave, you can put it on a variable autotransformer and slowly crank it up. Once the rectifier tube lights up enough to work...

I'm going to pass all of this advice onto my chum Ivan in the hopes that he will actually be making it work :-)

Max The Magnificent
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Re: Caps
Max The Magnificent   5/27/2014 9:16:35 AM
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@vandamme0: If you give up, don't throw out the case.

Ivan doesn't know the mneaning of the words "give up" LOL

Max The Magnificent
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Re: Anachronism
Max The Magnificent   5/27/2014 9:10:42 AM
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@perl_geek: I think you'll find that the radio dates from the mid 1950s, not the early 1940s.

I think you might be right -- I was going on what Charles said to me when he gave it to me.

Duane Benson
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Tube radios
Duane Benson   5/23/2014 7:41:24 PM
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I still have two tube radios. I've got a Hallicrafters S-38, 1940's (I think) vintage short wave radio. I haven't turned it on in a few years, but it worked just fine the last time I did.

I've also got a 1929 Atwater Kent TRF (tuned radio frequency) radio. Unfortunately, I don't have the cabinet. Just the radio. I haven't turned it on since about 1984, but it did work then. The sound wasn't so great after my rather lousy job of re-coning the speaker. I'm a little afraid to turn it on now, because of the old capacitors.

mlise
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No Problem
mlise   5/26/2014 1:10:14 PM
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Tube circuits are pretty easy to fix, even for a digital guy. Replace all the caps. Replace all the tubes.

Most of the coupling and filter caps can be replaced with 630 volt film caps. There's probably a chassis mounted single or multi-section electrolytic. Leave it in place, so you don't have an ugly hole. Just disconnect the positive end and use a modern cap underneath the chassis; it will be a lot smaller. Change the mica caps too, but leave the ceramics alone. If the radio pops through the speaker, it's moisture being driven from the ceramics and will go away.

NOS (new old stock) radio tubes are totally available, either from online tube stores or on e-bay, and cheap. As TV repair men pass away, their grand kids sell the garage full of tubes to a broker who is looking for the few specific make/model valuable audio tubes. The rest are TV and radio tubes or audio tubes with an unimpressive pedigree that are pretty much worthless. A lot of DIY guys are designing amplifiers with TV sweep tubes because they sound great and are cheap. Audio tubes are still in current production and are pretty cheap.

Generally you can do the fix without a schematic, but it's likely to be glued to the inside of the back. If there's no power transformer you have a 'Hot' chassis. You get a 50% chance of the chassis being at AC line. When a little kid pulls the knobs off, the metal shafts will be at AC line too, so replace the power cord with something polarized like an IEC-320 connector. Leave the ground disconnected, but you can at least get AC neutral on the chassis, assuming the building is wired properly.

 

Max The Magnificent
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Re: No Problem
Max The Magnificent   5/27/2014 9:17:43 AM
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@mlise: Tube circuits are pretty easy to fix, even for a digital guy. Replace all the caps. Replace all the tubes.

Well, that sounds easy enough LOL

salbayeng
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Re: No Problem
salbayeng   5/29/2014 6:08:26 AM
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@mlise: Tube circuits are pretty easy to fix, even for a digital guy. Replace all the caps. Replace all the tubes

And replace any resistors that look to have brown brown brown color bands.

(Tube radios don't use 110Ω resistors ! )

Max The Magnificent
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Re: No Problem
Max The Magnificent   5/29/2014 10:05:31 AM
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@salbayeng: Tube radios don't use 110Ω resistors !

You sound like this is a topic that's pretty close to your heart?

salbayeng
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Re: No Problem
salbayeng   5/31/2014 1:29:05 AM
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Yeh when I was ~8 yrs old, my schoolmates dad owneda  radio/TV repair business , we would go dumpster diving and wire up "radios" using old valves , (well we could get the filaments glowing anyway witha 6V battery !).

Built a Tesla coil (first of several) at age 15  used a 806? 810? triode (octal base with top cap anode) it used about 3 scavenged valve radio transformers to get the 1000v B+.   Made a friedd with a tech at the local radio station, he gave me some bigger valves (Used in sets of 4 as the exciters I think? they discarded the whole set when weakest valve couldn't keep up)

Not really done much with valves since.

The 110ohm observation was with a Chinese made hot air station, it had a handful of carbon composition resistors in the triac speed control. One resistor looked kind of heat stressed and was brown brown brown (and measured an erratic 63k)  , while another resistor of the same size nearby showed brown black orange and measured 10k. I swapped the suspect one with a 2W metal film 10k resistor and the speed control worked properly again.  

That sparked a recall from decades back with colleagues who had also noted propensity for drifts in carbon composition resistors that ran hot. By contrast modern metal film resistors can be cooked till the paint flakes off and show no drift.

On a related note , be wary of metal film resistors > 100k operated at 250v or more (The Tectronix SC501 tiny scope was always having trouble with a set of 4 voltage dividers on the HT) You need to replace with "high voltage" resistors, (and preferably physically bigger resistors as this lowers the electric field)

Max The Magnificent
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Re: No Problem
Max The Magnificent   6/2/2014 11:21:31 AM
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@salbayeng: On a related note , be wary of metal film resistors > 100k operated at 250v or more (The Tectronix SC501 tiny scope was always having trouble with a set of 4 voltage dividers on the HT) You need to replace with "high voltage" resistors, (and preferably physically bigger resistors as this lowers the electric field)

Good tip -- thanks for sharing

kfield
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Mysterious Object
kfield   5/28/2014 9:17:25 AM
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What's that white thing on the floor to the right of the radio? Some sort of sculpture of a head? I am just sure there's an interesting story behind it!

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   5/28/2014 9:34:16 AM
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@kfield: What's that white thing on the floor to the right of the radio? Some sort of sculpture of a head?

That's actually a carved wooden butler holding a tray -- it's closer than you think because it's actually stood right next to the big chair -- it holds my breakfast gin-and-tonic for me LOL

kfield
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Re: Mysterious Object
kfield   5/28/2014 9:40:45 AM
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@Max Oh, I thought you might be using it to serve elevenses!

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   5/29/2014 10:06:52 AM
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@kfield: I thought you might be using it to serve elevenses!

Ah, time for tiffin :-)

David Ashton
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Re: Mysterious Object
David Ashton   5/31/2014 2:14:51 AM
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@KField....  "Elevenses"....  reminds me of an Andy Capp cartoon (Andy Capp was a working-class British layabout forever shirking work, drinking beer and chatting up barmaids, and a cigarette hanging out of his mouth).  He had a long suffering wife called Flo who had cleaning jobs to bring in a bit of money.   I remember one cartoon with Flo carrying a tray of 11 beers to Andy, with the comment "Elevenses!"

I'm sure even Max would struggle with 11 G&Ts for breakfast.....

kfield
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Re: Mysterious Object
kfield   5/31/2014 2:14:32 PM
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@DavidAshton I'm not so sure whether Max would struggle with elevenses, did you see the pictures of him during the EE LIVE! pub crawl? He was going strong late into th evening...

David Ashton
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Re: Mysterious Object
David Ashton   5/31/2014 9:14:51 PM
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@Kfield...."did you see the pictures of him during the EE LIVE! pub crawl?"

No...you got a link??

Good to know I will have some competition if I make to to EELive 2015.....

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 11:26:15 AM
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@David: ...I will have some competition if I make to to EELive 2015

You flatter yourself LOL

Sheepdoll
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Be careful what you ask for
Sheepdoll   6/2/2014 1:04:14 PM
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@David Ashton No...you got a link??
I have a selfie I took.  Too much gingerale that evening.

EELive pub crawl

David Ashton
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Re: Be careful what you ask for
David Ashton   6/2/2014 4:40:26 PM
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@Sheepdoll....looks good....I'm a big fan of gingerale myself.....

David Ashton
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Re: Be careful what you ask for
David Ashton   6/2/2014 4:43:10 PM
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@Sheepdoll more importantly HOW did you post the pic?   I fail miserably when I try.  It only seems to work if you post it somewhere on the net first and then put in the URL - is that what you did?

(Thinks - maybe I should try it when I have had a few ginger ales....)

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 11:27:19 AM
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@kfield: He was going strong late into the evening...

Alcohol never touched my lips! LOL

Stargzer
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Re:Alcohol never touched my lips! LOL
Stargzer   6/2/2014 3:37:51 PM
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@Max

Used a straw, eh?

:-Þ

Max The Magnificent
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Re:Alcohol never touched my lips! LOL
Max The Magnificent   6/2/2014 4:06:22 PM
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@Stargzer: Used a straw, eh?

No -- just tilted my head way back and poured it quickly LOL

kfield
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Re: Mysterious Object
kfield   6/2/2014 5:48:56 PM
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@Maxthemagnificent  You mean you were pouring it directly down your gullet, bypassing your lips entirely?

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 5:58:02 PM
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@kfield: You mean you were pouring it directly down your gullet, bypassing your lips entirely?

Well, that's the underlying meaning when you say "alcohol never touched my lips" ... but you do understand it's a joke -- right?

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 5:59:24 PM
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@kfield: ... but you do understand it's a joke -- right?


Otherwise how would I have been able to suck up any that accidentally sloshed onto the table? LOL

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/3/2014 9:45:12 AM
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@kfield: You mean you were pouring it directly down your gullet, bypassing your lips entirely?

Hey -- I'm not gauch -- my mom brough tme up propper -- I know which color drinking straws and which paper umbrellas go with each type of cocktail -- and when it comes to a formal dinner in which white, red, and dessert wines are served with each course, I know that you use the drinking straws starting from the outside -- LOL

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 11:22:26 AM
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@David: I'm sure even Max would struggle with 11 G&Ts for breakfast.....

Is that a dare?

David Ashton
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Re: Mysterious Object
David Ashton   6/2/2014 4:47:55 PM
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@Max hmmmm....go right ahead but I don't think I'd quite keep up with you.  I had 9 G&T's once and then DROVE round (this was way in the past...)  to my then girlfriend's place and later went to sleep.  I can't have been that bad 'cos she is now my wife.  But she has not let me forget that.

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 4:55:13 PM
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@David: I had 9 G&T's once [...] drove to my then girlfriend's place [...] she is now my wife.

A warning to us all as to the dangers of alcohol! LOL

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 4:56:20 PM
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@David: But she has not let me forget that.

Strange how wives and mothers forget all of the good things you do, but you blow up one lousy garage and...

Max The Magnificent
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Re: Mysterious Object
Max The Magnificent   6/2/2014 11:25:08 AM
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@David: ...reminds me of an Andy Capp cartoon...

I remember reading those when I lived in England -- they were on what the Americans woudl call "The Funny Page(s)" of the Daily Mirror and Sunday Mirror newspapers.

Stargzer
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Re: Andy Capp
Stargzer   6/2/2014 2:36:17 PM
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ADavid Ashton

Andy Capp is alive and ... well, he's well between the football matches.

He appears in various US newspapers (there still some in print) but you should be able to find him, Flo, and the others at Comics.com.  Alas, that's one site embargoed by our net nanny software, the same software that wouldn't let me access a site for the famous WWI infantry unit known as "The Fighting 69th."

Sic semper whatever ...

Stargzer
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Re: Andy Capp
Stargzer   6/4/2014 12:53:51 PM
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@David Ashton: "(Andy Capp was a working-class British layabout forever shirking work, drinking beer and chatting up barmaids, and a cigarette hanging out of his mouth).  He had a long suffering wife called Flo who had cleaning jobs to bring in a bit of money."

Andy resides at gocomics.com.  Here's today's story:

 

Edit: The picture doesn't show on my PC, but I don't know if it's our net-nanny software or not.

Max The Magnificent
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Re: Andy Capp
Max The Magnificent   6/4/2014 3:38:44 PM
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@Stargzer: The picture doesn't show on my PC, but I don't know if it's our net-nanny software or not.

It shows on mine when I click your link...

 

calasus40
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Check my book shelf
calasus40   5/28/2014 9:28:55 AM
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I will see if this radio is in the books I have. I acquired a bunch of repair items a few years back on radios and tvs. Give me a week or two to try and locate it.

Max The Magnificent
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Re: Check my book shelf
Max The Magnificent   5/28/2014 9:36:11 AM
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@calasus40: I will see if this radio is in the books I have. I acquired a bunch of repair items a few years back on radios and tvs. Give me a week or two to try and locate it.

My chum Javi Garcia found the scxhematics as a PDF online, but if you have a full up book that woudl be even better (assuming you wish to donate it to the cause, of course :-)

perl_geek
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Manuals
perl_geek   6/4/2014 3:29:37 PM
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Check the links in my earlier posting. That's why I put them in.

Max The Magnificent
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Re: Manuals
Max The Magnificent   6/4/2014 3:36:47 PM
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@perl_geek: Check the links in my earlier posting. That's why I put them in.

I'm going to -- just as soon as a get a moment to draw breath :-)

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