Hi folks,Just out of curiosity,I tested the plate voltage on the 6f6 output tube on my re-capped Hallicrafters s-40a.None of the radio's resistors were replace by the yo-yo that I hired to restore this chassis.He claimed all voltages were within spec.The plate voltage reads 315 volts,much higher than the 235 claimed by sam's photofact or 250 by Hallicrafters.This did not surprise me in that the resistors in this set are going on 60 years old and the guy was a schmuck.I then put the radio back in the cabinet.
Just for giggles I plugged in my Philco 37-610b and took out the 6f6 and measured the plate voltage(I was too lazy to take the chassis out).I expected to have a very close reading to the philco spec of 255 volts.I completely rebuilt this chassis with all new caps and resistors,and imagine my surprise when I got a reading of 415 volts!Would taking the 6f6 out of circuit cause such a huge variance in plate voltage?Also,on the Hallicrafters,if the power resistors in the power supply have drifted up in value,as I always find them to do on other radios,would this make the plate voltage go up instead of down?I believe on the Hallicrafters,taking the tube out made no difference in plate voltage or very little.Finally,could this all be the final excuse I need to go out and get that new Fluke DVM I have been wanting to replace that Taiwanese Radio Shaft wonder I have been using?Any thoughts appreciated.Thanx.

Well today's line voltagee are a little higher. What are the voltages when the set is warmed up and playing? Usualy the voltages will be close with ALL tubes in the right place drawing current. Maybe some one else can elaborate some more, or maybe point out a problem that i'm unfamiliar with.
Jeremy

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:Hi folks,Just out of curiosity,I tested the plate voltage on the 6f6 output tube on my re-capped Hallicrafters s-40a.None of the radio's resistors were replace by the yo-yo that I hired to restore this chassis.He claimed all voltages were within spec.The plate voltage reads 315 volts,much higher than the 235 claimed by sam's photofact or 250 by Hallicrafters.This did not surprise me in that the resistors in this set are going on 60 years old and the guy was a schmuck.I then put the radio back in the cabinet.
: Just for giggles I plugged in my Philco 37-610b and took out the 6f6 and measured the plate voltage(I was too lazy to take the chassis out).I expected to have a very close reading to the philco spec of 255 volts.I completely rebuilt this chassis with all new caps and resistors,and imagine my surprise when I got a reading of 415 volts!Would taking the 6f6 out of circuit cause such a huge variance in plate voltage?Also,on the Hallicrafters,if the power resistors in the power supply have drifted up in value,as I always find them to do on other radios,would this make the plate voltage go up instead of down?I believe on the Hallicrafters,taking the tube out made no difference in plate voltage or very little.Finally,could this all be the final excuse I need to go out and get that new Fluke DVM I have been wanting to replace that Taiwanese Radio Shaft wonder I have been using?Any thoughts appreciated.Thanx.

WHY, 'soitanly .......one should expect that plate voltage at that pin to be sky high!
Without that major consumer of the power in your radio, the Audio ouput tube, in circuit, the power supply is not being loaded down with normal current being
consumed with the adjunct dropping of the plate voltage supply level.
Unless the filter capacitors were also conservatively voltage over rated one might encroach upon them also going ballistic, at high voltage subjecture.
I have plug in adapter sockets to plug tubes into and then be able to take a voltage reading at corresponding terminals atop the adapter.
HOWEVER there is a satisfactory El Cheapo technique of merely taking a length of bare buss wire and fashioning it around a tube pin a few turns and then route it
upwards beside the tubes base. Fashion a second loop there and bind the unit tight with a rubber band twirled about the base. Then you can plug in the tube for test
and take a voltage test at your test loop with your meter test probe. Pull the tube and walk the loops pin position on around to other pins if necessary for other readings.

73's de Edd

Pee Ess:
Go out and get the FLUKE.......Duke.
Just for the Hades of it.
....You'll enjoy it !

In agreement with MR. EDD. It is not a good practice to pull tubes or speaker plugs and measure voltages. But you can do this if you like the smell of capacitors smoking or the wonderful tin foil and haze effect. Just because resistors are old does not mean they are defective. Just a check in their tolerance is usually all that is needed +/- 20% or +/- 10% if you are picky. Sometimes, though, you will get a noisy resistor. The power supply in most radios is not regulated so any change in load (tube removal, line voltage changes etc.) will cause a change in voltage readings. Hope this has been helpfull...... Merry CHRISTmas

MRO

Again, I have to totally emphasize what Edd said. You shouldn't take voltage readings with resistors removed. Generally, unless a resistor is shunting across the power supply, if it drifts, voltages will get lower after it. Typically resistors are in series with the power supply and a tube, not directly across the power supply. If it drifts, and it's loading across the power supply, voltages throughout the radio will get higher. Also, if a resistor on one tube drifts high and reduces the voltage to that tube, voltages throughout the rest of the radio may go higher.

Another thing to keep in mind if you take voltage readings with the tubes in place (the only way to take working voltage readings) is that weak tubes will cause the voltages to get higher. If the tubes are not drawing enough curent, voltages will rise in an unregulated power supply (typical of old radios). If the rectifier gets week, however, the voltages will go lower. If your 6L6 or 6F6 is weak, voltages in its circuit will be higher.

If the guy who repaired your radio did not find any of the resistors to be drifted, then he should not have replaced any. Most radio repairmen don't. For one thing it's not necessary (it is much more important to replace capacitors even if they are not faulty now). Resistors are easily replaced, and if they haven't already gone, they probably won't go in the near future. Another thing is that the old style resistors in the older radios are not easy to find. Old radios are not simply pieces of electronic equipment. They are antiques. Sadly there are people who don't think this way, and just replace everything. Years from now after all of the radios have been altered, people will not be able to see what a wiring job of the 1930s and 40s looked like. There are methods and materials available that allow you to keep the underside of a radio looking fairly original, while still allowing you to make the radio function perfectly.

Thomas

Thanx for all responses.Firstly,this is the only time I have taken voltage measurements without tubes in place.It seems I remember reading somewhere that this was a no-no.The only reason I checked is because the guy who worked on this radio shagged me so badly I just knew the voltage readings would be way out,meaning out of spec resistors were still in place in the radio.Originality on this radio,or most any radio, under the chassis means little to me.A radio of any vintage, to me, is a tool to be used.I wanted the radio to be as trouble free as absolutely possible.He agreed to check all resistors and replace any, more than 15 to 20% out(and believe me,for what he charged,he should have).This radio uses the same big dogbone resistors in the power supply as the old Philco radios that I have.In the Philcos,pretty much all of these were grossly out of spec,35% and much more.I will bet dollars to dognuts when I finally tear into this radio and start testing resistors (in other words finishing his job for him),I will find many well outside of twenty percent.I assume that this will get the voltages back where they belong,because even with the 6f6 in place,the plate voltage was nearly as high.I find it hard to believe that Mr.Restorer didn't notice this,unless of course he didn't bother to check,which likely is the case.This is why I took you folks' advice and started doing my own work.Also,thank you Edd.All I was waiting for was one person to tell me that the new Fluke was a good move ,so I can tell my conscience it wasn't just "my"idea.As always,thanx for your time.

Some of the resistors may very well be out of tolerance. However, if a radio is only a tool for you, perhaps you should buy a new one. They usually work as soon as you buy them.

Thank you Thomas for your smug reply.I know when I try to make a serious point,at least one person has to chime in with a smart-ass comment.My two main points were that I like to get what I pay well for and "under chassis" originality is not important to me,a radio that works well,antique or not,is.And I have several brand new digital gee wizz radios too!Thanks!!!!!

:Thank you Thomas for your smug reply.I know when I try to make a serious point,at least one person has to chime in with a smart-ass comment.My two main points were that I like to get what I pay well for and "under chassis" originality is not important to me,a radio that works well,antique or not,is.And I have several brand new digital gee wizz radios too!Thanks!!!!!

I just hope you didn't pay your "alledged" tech too much money. There are so many out there calling themselves techs and lacking basic electronics knowledge. You're not the first and last victim, unfortunately.

Fluke manufactures very good test equipment. That said, I wouldn't change my 15 yo Micronta bench DMM...

Z-

Thanks. I am very passionate about restoring a radio or antique electronic device to as authentic a condition as possible, as everyone on here seems to know (I'm not quiet about it). Good luck with your project, though. Hopefully all of the voltages will turn out right once you get all of the resistors in order.

Hi:
I don't know which "Taiwanese Radio Shaft wonder" you actually have or its condition... but unless it's damaged or a real cheap "toy" or maybe ifit is a $5 analog meter with a hard to read scale... I can't see how any another meter will make that big of a difference.
Is the Radio Shack meter analog or a digital?

I know Fluke makes good test equipment but I can't imagine that any other meter will read drastically differently unless yours is damaged.

Peter,The meter is a digital unit.It has been damaged in that half of the functions no longer work.I read an article concerning the accuracy' or lack of, concerning some dvm's,and this model was near the top of the list(made about ten tears ago).In fact,the reviewer once said he was given one as a gift and he was so unimpressed with its accuracy,he threw it away.As far as the new Fluke goes,I was only jokeing about needing an excuse to buy it.Its already on its way.That's the great thing about being single-you can have Christmas all year 'round!

Bachelor-dom...
Here Here.. 3 cheers to that!!!
I have to chuckle a bit when I think of friends who can't even relax while working on their radio hobby for fear that the "little lady" might admonish them past a certain hour... so sad..

I've been single since 1978...lol
...it's very nice when the ladies do spend the evening here ... but it's also very nice when they go home...lol ;-)

Meters:
I'm not defending radio shack but I've bought stuff there I have no complaints about.
A DMM model 22-813... that works great.. and another one made by Extech 22-816... that works fine too... got it cause it has a capacitance cheker..
I use them both all the time everyday.. no problems ever yet.