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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 15th Feb 2020, 12:56 am   #21
joebog1
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Default Re: New gear

Last few pics before I test to see if the magic smoke is ready to stampede.

The warranty seal was unbroken before I broke it to check.

Quality is highly apparent, especially in that superb 4 gang tuning cap.

I will let you know how I go. The other three units are in a very poor state, although I will try and recover the attenuator as it doesn't contain a power supply, and for some reason appears to be much less corroded.

Joe
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Old 15th Feb 2020, 2:57 pm   #22
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How bad is the 209A inside?

David
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Old 16th Feb 2020, 1:50 am   #23
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Seems the 209A is OK. There is some corrosion but it seems limited to the spacers that are used and the shafts of the switches. I cannot "see" any water damage in fact. The PCB's are not as shiny as I would expect but that could be OK considering the age of the unit. Also extremely difficult to photograph.

The range switch is seized solid !!! The absence of a knob, and careful examination of the shaft indicates that somebody used large pliers in an attempt to rotate the shaft.
I have it soaking in a drop of RP7. I will keep you informed.

I would like to remove the main PCB but I cannot remove what I think are grub screws in the front panel knobs. Are the grub screws themselves covered or are they just full of crud? I cannot find anything in the manual regarding them.

Joe
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Old 17th Feb 2020, 11:55 pm   #24
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So I have discovered that HP actually cover the grub screws with either a plug, or a dob of black silicone to hide the grub screws. I have managed to remove this cover and I find I dont have an Allen key the right size. Can anybody tell me please? I have a fair collection of small Allen keys but this size escapes me.

Thanks in advance

Joe
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Old 18th Feb 2020, 8:46 am   #25
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It is an American product, so the allen keys will be imperial not metric. I keep a set of both, because much of my test gear is Tektronix, General Radio and HP. The key thing (ha ha) is not to mix up the metric and imperial keys.

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Old 18th Feb 2020, 8:58 am   #26
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Craig!!! I also play with two wheel and four wheel transportation mobiles. I have MANY sets!! ( some are incomplete ) I DONT have one that fits. Be it imperial or metric.
REMEMBER a ton is a real ton in blighty as in Australia its 2240 lbs, NOT a short ton, 2000 lbs.
WE also have a REAL gallon, not 3.7 litres or whatever is the short gallon.
ALL the HP stuff I have has Allen key screws fitted to the knobs. I have an Allen key for ALL the other HP gear I own. This is all sand gear not vacuum, so perhaps its washed away in the sand pit ?
Seriously I need order an Allen key and I want the right one.

Joe
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Old 18th Feb 2020, 9:25 am   #27
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Default Re: New gear

Some were 'Bristol Spline' as well.

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Old 18th Feb 2020, 10:02 am   #28
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I actually had to look that one up! Never seen them in any of my old-skool gear, though

Craig
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Old 18th Feb 2020, 12:08 pm   #29
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Quote:
Originally Posted by Craig Sawyers View Post
It is an American product, so the allen keys will be imperial not metric. I keep a set of both, because much of my test gear is Tektronix, General Radio and HP. The key thing (ha ha) is not to mix up the metric and imperial keys.

Craig
RS do (or did) two nice sets of hex drivers, one imperial and one metric, with the size clearly marked on the handle. I've found them invaluable in cases of brain fade...
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Old 18th Feb 2020, 7:51 pm   #30
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Quote:
Originally Posted by joebog1 View Post
So I have discovered that HP actually cover the grub screws with either a plug, or a dob of black silicone to hide the grub screws. I have managed to remove this cover and I find I dont have an Allen key the right size. Can anybody tell me please? I have a fair collection of small Allen keys but this size escapes me.
HP used UNC grub screws, below are the sizes & appropriate Allen keys.

#8-32, 5/64"
#6-32, 1/16"
#4-40, 0.05" (50 thou)

They sealed up the holes for the grub screws in the knobs as the inner (shielded) chassis on some HP test gear is not grounded (earthed), the shafts can be at the same potential as the voltage source the test gear is connected to.
There were also modification kits to change all of the knobs for collet lock types, I'm not convinced these are any safer as the knob caps are often missing.

David
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Old 18th Feb 2020, 9:39 pm   #31
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I guess sometimes things happen in the right way.
Yesterday I was given this lot of clobber. I will be refurbishing most of it in the next weeks.
I am very envious, I wish someone would give me similar

David
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Old 18th Feb 2020, 11:44 pm   #32
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Factory, Thanks for your answer, but I have tried the sizes you suggest and unless its a different shape to a normal Allen key, they dont fit. 50 thou dont fit ( too small) and 1/16" is too large. I have tried more than one grub screw

Joe
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Old 19th Feb 2020, 7:25 am   #33
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Good idea to give em a soak in something Joe. Every Tek or HP bit of gear I've come across have at least one knob where a flame thrower or small nuclear warhead is needed to shift the grubscrew.

"I am very envious, I wish someone would give me similar" they can still be picked up cheap, I got one from the BVWS auction for a fiver, or was it £30? Also Stewarts of Reading have several and they come up on ebay for a about a ton.

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Old 20th Feb 2020, 12:03 am   #34
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I dont know if I am losing it or what.
403B AC voltmeter and 350D attenuator both have 1/16" Allen keyed knobs. Both insulated as I previously explained.
209A audio oscillator does not!!! Actual size is smaller than 1/16" but larger than 50 thou. 75 thou ? I have never heard of that size before.

Joe
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Old 20th Feb 2020, 6:02 am   #35
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Isn't 1/16" is 62.5 thou? So a 75 thou Allen key would be even larger. Maybe 60 thou, but I've never seen that one either. 1/16" is around 1.6mm, does a 1.5mm key fit (that is a standard size)?

The small Imperial size Allen keys that I've seen are 28 thou, 35 thou, 50 thou and then 1/16". For metric sizes, they're 0.7mm, 0.9mm, 1.3mm and 1.5mm. The first 3 of those are actually rounded approximations to the actual sizes of the keys which turn out to be the same as the smallest 3 Imperial ones (that said, one tool company has different part numbers for 0.05" and 1.27mm Allen key blades....)

Are you sure it's Allen hex? Bristol Spline is a possibilty as others have said. I've got an instrument (not HP) where all the knobs are Allen hex apart from the turns counter dial on a 10 turn potentiometer, which is Bristol Spline.
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Old 20th Feb 2020, 8:08 am   #36
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To all patient and helpful persons!!!!

The reason the Allen keys dont fit is the thickness of the corrosion!!! They ARE in fact 50 thou Allen keys, but the corrosion is so hard and so thick I have been loath to hammer the sh*t out of the screws to remove them.
My initial comments being about "swimmers" ( been in a flood or tidal wave) I still hold with.

I did say I would try revive the 350D attenuator first.
I have since done this. ( see the pic).
Corrosion is ALWAYS on the zinc plated ( ? ) parts. ( I have checked all three sand units).
I have always understood that zinc was ( fairly) immune to atmospheric corrosion, ESPECIALLY inside a superbly made instrument case. Switch shafts and switch spacers ( between banks) are THICK!!.
I mean a switch shaft of nominal 1/4" is MUCH closer to 3/8" thick. FURRY !! much bigger than my meager beard!!.

Some scraping and vigorous wire brushing has cleaned up the attenuator, so much so I didnt take pics of its internals. A new set of 3/4" binding posts
( ALL of them were smashed, requiring sidecutters to remove the debris) from China completes the rebuild.
Actual testing will be tomorrow, but switches now rotate with silk smoothness and positive indentations. Those scratches on the front panel were
bequeathed along with the equipment.
Bottom knob was smashed into three pieces by Generous Knob Twiddlers and twisted into three separate pieces. Some superglue helped, but I need a new( 2nd hand ) replacement knob.

Thanks to all readers and helpers again!!

Joe
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Old 20th Feb 2020, 8:39 pm   #37
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Originally Posted by TonyDuell View Post
Are you sure it's Allen hex? Bristol Spline is a possibilty as others have said. I've got an instrument (not HP) where all the knobs are Allen hex apart from the turns counter dial on a 10 turn potentiometer, which is Bristol Spline.
There is a lot of vintage HP test gear in my collection and I have only seen the three common sizes of grub screw (previously mentioned) used for the control knobs.
I've only came across a single Bristol Spline grub screw on HP test gear and yes it was on a counter dial (on a HP 105B).

As the grub screws are often in poor condition, either due to corrosion or incorrect Allen keys having been used, I ordered plenty of new stainless steel grub screws in #4,#6 & #8 UNC to replace any knackered ones I find.

David
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Old 20th Feb 2020, 8:45 pm   #38
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Bottom knob was smashed into three pieces by Generous Knob Twiddlers and twisted into three separate pieces. Some superglue helped, but I need a new( 2nd hand ) replacement knob.

Thanks to all readers and helpers again!!

Joe
Those knobs on the 350D aren't the originals (in fact I have no idea who made those), they would have been grey the same as the terminals were. The later grey knobs seem a lot more fragile than the older ones.
I attach a picture of how your 350D attenuator would have looked.

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Good luck with the other two, hopefully you can repair them.

David
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Old 20th Feb 2020, 10:35 pm   #39
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factory,
the knobs have HP part numbers silk screened or etched into the steel insert inside or behind the knob. Yes I think I will be able to repair the other two, PROVIDING the units havent been under water. Transformers and water dont mix very well. Also they are too small for me to rewind these days. Im getting a little shaky :-}.

I am still surprised to find that the only "bits" that are really corroded are switch parts.
Shafts are very corroded, as are clicker plates, spacers and mounting collars. Unless they werent passivated , a bad batch of plating I am a bit lost as to why only the switches are crook. All the pots still work smoothly.

Joe
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