Good video Jim as always. I also have a Heathkit IM-11 like you, and a Heathkit EUW-24 (yours is an IM-13). The EUW-24 is an horizontal VTVM like the IM-13 you have there. So the similarity between your setup and mine is obvious. In my case, both schematics are exactly the very same between them to the slightest detail. Funny thing is than the EUW-24 was sold already assembled by Heathkit and was part of the "Laboratory" series that made it better "laboratory grade" and way more expensive too..... But the schematic and circuitry is exactly the very very same to the one sold as a kit. Just an observation about sound... your voice is OK, calm and soft, good the ears... but the sound of things falling on the bench (like the test leads) or any other sound in the shop, like you throwing tools on the bench sound extremely high (I am using headphones). Your ambient mic is very sensitive. You can even hear the ball bearings of the Lazy Daisy you have on the bench when you turn around equipment on top of it. Since you are filming almost every day, I would recommend passing the sound through a compressor. That way the compressor will limit the surges in sound from things banging on the desk and will boost your voice to a nice all out level. Enjoyed the video. 73 Roberto YS1RS
Interesting video on these units. I am planning on picking some up for restoration and possibly use on my bench. I just finished rebuilding an EICO 232 myself. The issues I noticed with those is that the 1% resistors used in the resistor ladders have drifted over time. They are the cap-type and have a bad habit of going open if the leads and caps are disturbed too much. I also designed a little PCB with a LM317 to replace the battery, powered from the 6.3VAC filament voltage. At some point I need to put together 2 new sets of 1% resistor sets to over-haul the resistor ladders, probably adding trimmers to dial them in.. The high resistance 1W resistors are hard to find these days though... Cheers, - Eddy
Older video I know, modern PSU's use a negative coefficient thermistor to slow the in rush current while the trans core and caps charge. Might also work in your case.
50:00 With these instruments, don't worry about the inrush current through the rectifier diode into the electrolytic filter capacitor upon power-up: the small power transformers in both will limit the current to a safe value because of their moderately high impedance. Both the primary and secondary windings have a DC resistance. Added to that is the inductive coupling losses between the windings. I'd replace the rectifier diodes in both with a common 1N4005 diode. They will love you long time. The 'lytics? I'd go with 22uF 150V.
Your IM-11 dates to 1961-1968 and the IM-13 1963-1968. Both were updated and replaced. I'll leave a link with information about Heathkit kits below. The older schematics used a horizontal line to indicate chassis ground. Later on that was replaced with a horizontal line with two consecutively shorter lines beneath, Earth ground was represented with a horizontal line and 5 or so diagonal lines below (like a rake). I usually order all my capacitors and resistors based on the parts list in the manual and have spares ready when I open it up. That 1600 volt cap is merely the safety coupling cap for the A.C. measurements. If you replace it with say a 1000v cap make a note not to try and measure A.C. over 800 volts or so.You may want to get manuals from the "New Heathkit Website they sell vintage manuals. Here are some links. I've ordered a few from them, but no delivery yet. Web site for Heathkit manuals, shop.heathkit.com/page/vintage-replacement-manuals A nice site with a lot of Heathkit Info. www.nostalgickitscentral.com/heath/heathkit.html
The little stand was meant for cell phones. I have bent the arms outward to accommodate my meters and in doing so, I broke off the little hands by accident. I don't know where I got them from - too many years ago now.
Stringing resister is usually done to increase voltage handling capability. The typically the voltage handling of 1/4 watt carbon-comp resister is 250v. Something not typically talked about.
I disagree. Looking at the specs sheets. Quarter watts resistors with normal ambient temperatures have a maximum voltage of 150 VDC. Operational temperature ranges are between -55 to 150 degrees celsius. I use carbon film for resistors above 2.5 k exclusively as they have working voltages at 2k and above.
All the data sheets I've seen, including Allen Bradley's own, give 1/4 a maximum working voltage of 250v with a 400v overload and 500v dialectic strength.(DC/RMS) I don't know which data sheet your information is from, but it appears that manufacture is more conservative than is common.
@@mjr1999 May I suggest you do further reading. Try ResistorGuide, Farnell, Vishay, or even Wikipedia. Only a few companies like Arcol stick to 250 degrees Fahrenheit for the total line. I guess you can take 250 as a rule of thumb, but it is not accurate for all carbon composition resistors. Farnell and Vishay are American manufactures of passive components.
@@JosephLorentzen We're talking about a meter that was designed in the 1950's or early 1960's. Yes there maybe modern forms of carbon comps that have different ratings, but checking Omhite, Farnell, Multicomp, they still rate there A.B. 1/4watt's for 250v.
Old capacitor specs: WV = Working Voltage - Voltage that capacitor is designed to handle on a long term. These caps may also show a spec for "Surge Voltage" - An overvoltage that the cap can tolerate for short times. This allowed for voltage to go high while things warmed up and pulled voltage down to normal. Modern capacitors do NOT have a surge capacity. They will break down if voltages above their marked value are applied. When replacing an old cap with a surge rating use one with a value equal or greater than the surge value. If dealing with transformer power supplies the voltage can go high quite easily. Measure if unknown and use a cap of value over peak voltage. Usually speaking, things like series circuit radios, phonos, etc. will not have such issues although you may find that items made before 1940 have capacitors with very high working voltage ratings of 350VDC or so. Modern circuits and their capacitors, including those made post WW2 will have more normal ratings of 150 volts or so. Surge ratings were dropped when solid state circuitry became the norm. Solid state rectifiers and power supplies did not go crazy when first turned on unless something had failed.
I think I get it now. WV is the expected maximum voltage that the capacitor will be expected to work at normally. Secretly, those old capacitors could sustain a higher voltage for a short period to accommodate power supply start up making that the 'real' rating. But to avoid confusing everyone, the manufacturers settled on the term 'working voltage' to state the rating during 'regular' service. Since modern equipment no longer has this startup problem with high voltages, components are no longer rated with that in mind and now the 'real' rating is printed on the capacitor and that should be considered a hard upper limit. I'd have to guess that the manufacturers still incorporate a lot of head room in these ratings or their component failure rate will be too high and sales would be impacted.
It is probably OK. I doubt that this is so old that the caps are of the reserve type and the draw of the tubes requires a ton of power. That transformer is pretty small. I'd worry more if there was an output amp putting out a watt or more. You can check it by measuring the rectifier voltage when it is first powered on with the caps in place. If it is below 160 you would be OK. If it goes above I would go with 200v or 250v caps. I would expect things to stay OK with 160v caps, especially if they are higher MFD than the originals. The time it takes for the caps to charge should keep things down till the tubes start conducting.
White, brown, gold, gold...9.1 ohm 5% carbon composition resistor. First gold band is 0.1 multiplier. Colors looked fine to me. Look for 9.1 ohm resistor in battery circuit.
Your iso-transformer should have an own fuse. And with any overload on the secondary side of the iso-trans the fuse on the primary side should and must break the current. Your home fuse should not be envolved. If it reacts, your installation has an error somewhere. But you live in danger. Really. You have a cable, where on one side is the main plug and on the other side are two crocodiles. I hope for you, you will never never be confused and work with this cable.
Yes that crocodile cable is risky to use. Wait until you see how I use it in the next video. Putting a fuse in the secondary of my isolation transformer strikes me as a good idea. I can never know, until it's too late, if shorting the isolation transformer secondary will draw enough to open the house circuit breaker. If not, something is liable to burn up including my house. If I were to leave my shop even briefly and that short circuit/fire scenario started, I might find my bench on fire and my house full of poison smoke in a minute. Now I'm motivated. Thanks for making me think about this a little further.
Good video Jim as always.
I also have a Heathkit IM-11 like you, and a Heathkit EUW-24 (yours is an IM-13). The EUW-24 is an horizontal VTVM like the IM-13 you have there. So the similarity between your setup and mine is obvious. In my case, both schematics are exactly the very same between them to the slightest detail. Funny thing is than the EUW-24 was sold already assembled by Heathkit and was part of the "Laboratory" series that made it better "laboratory grade" and way more expensive too..... But the schematic and circuitry is exactly the very very same to the one sold as a kit.
Just an observation about sound... your voice is OK, calm and soft, good the ears... but the sound of things falling on the bench (like the test leads) or any other sound in the shop, like you throwing tools on the bench sound extremely high (I am using headphones).
Your ambient mic is very sensitive. You can even hear the ball bearings of the Lazy Daisy you have on the bench when you turn around equipment on top of it.
Since you are filming almost every day, I would recommend passing the sound through a compressor. That way the compressor will limit the surges in sound from things banging on the desk and will boost your voice to a nice all out level.
Enjoyed the video.
73
Roberto
YS1RS
Interesting video on these units. I am planning on picking some up for restoration and possibly use on my bench.
I just finished rebuilding an EICO 232 myself. The issues I noticed with those is that the 1% resistors used in the resistor ladders have drifted over time. They are the cap-type and have a bad habit of going open if the leads and caps are disturbed too much. I also designed a little PCB with a LM317 to replace the battery, powered from the 6.3VAC filament voltage.
At some point I need to put together 2 new sets of 1% resistor sets to over-haul the resistor ladders, probably adding trimmers to dial them in.. The high resistance 1W resistors are hard to find these days though...
Cheers,
- Eddy
Older video I know, modern PSU's use a negative coefficient thermistor to slow the in rush current while the trans core and caps charge. Might also work in your case.
50:00
With these instruments, don't worry about the inrush current through the rectifier diode into the electrolytic filter capacitor upon power-up: the small power transformers in both will limit the current to a safe value because of their moderately high impedance. Both the primary and secondary windings have a DC resistance. Added to that is the inductive coupling losses between the windings.
I'd replace the rectifier diodes in both with a common 1N4005 diode. They will love you long time. The 'lytics? I'd go with 22uF 150V.
Your IM-11 dates to 1961-1968 and the IM-13 1963-1968. Both were updated and replaced. I'll leave a link with information about Heathkit kits below. The older schematics used a horizontal line to indicate chassis ground. Later on that was replaced with a horizontal line with two consecutively shorter lines beneath, Earth ground was represented with a horizontal line and 5 or so diagonal lines below (like a rake). I usually order all my capacitors and resistors based on the parts list in the manual and have spares ready when I open it up. That 1600 volt cap is merely the safety coupling cap for the A.C. measurements. If you replace it with say a 1000v cap make a note not to try and measure A.C. over 800 volts or so.You may want to get manuals from the "New Heathkit Website they sell vintage manuals. Here are some links. I've ordered a few from them, but no delivery yet.
Web site for Heathkit manuals, shop.heathkit.com/page/vintage-replacement-manuals
A nice site with a lot of Heathkit Info. www.nostalgickitscentral.com/heath/heathkit.html
No worries about ESR on those filter capacitors Jim!!!!
that c-3 cap tester places around 55 volts a/c to test the capacitor value.
Who Played Marie Curie?
Another interesting video Jim, thank you. Where did you get the multimeter stand/feet?
The little stand was meant for cell phones. I have bent the arms outward to accommodate my meters and in doing so, I broke off the little hands by accident. I don't know where I got them from - too many years ago now.
Stringing resister is usually done to increase voltage handling capability. The typically the voltage handling of 1/4 watt carbon-comp resister is 250v. Something not typically talked about.
I disagree. Looking at the specs sheets. Quarter watts resistors with normal ambient temperatures
have a maximum voltage of 150 VDC. Operational temperature ranges are between -55 to 150 degrees celsius.
I use carbon film for resistors above 2.5 k exclusively as they have working voltages at 2k and above.
All the data sheets I've seen, including Allen Bradley's own, give 1/4 a maximum working voltage of 250v with a 400v overload and 500v dialectic strength.(DC/RMS)
I don't know which data sheet your information is from, but it appears that manufacture is more conservative than is common.
@@mjr1999 May I suggest you do further reading. Try ResistorGuide, Farnell, Vishay, or even Wikipedia.
Only a few companies like Arcol stick to 250 degrees Fahrenheit for the total line.
I guess you can take 250 as a rule of thumb, but it is not accurate for all carbon
composition resistors.
Farnell and Vishay are American manufactures of passive components.
@@JosephLorentzen We're talking about a meter that was designed in the 1950's or early 1960's. Yes there maybe modern forms of carbon comps that have different ratings, but checking Omhite, Farnell, Multicomp, they still rate there A.B. 1/4watt's for 250v.
@@mjr1999 Not necessary true according to the data sheets, but use it as a rule of thumb unless you look it up.
Old capacitor specs:
WV = Working Voltage - Voltage that capacitor is designed to handle on a long term.
These caps may also show a spec for "Surge Voltage" - An overvoltage that the cap can tolerate for short times. This allowed for voltage to go high while things warmed up and pulled voltage down to normal.
Modern capacitors do NOT have a surge capacity. They will break down if voltages above their marked value are applied. When replacing an old cap with a surge rating use one with a value equal or greater than the surge value. If dealing with transformer power supplies the voltage can go high quite easily. Measure if unknown and use a cap of value over peak voltage.
Usually speaking, things like series circuit radios, phonos, etc. will not have such issues although you may find that items made before 1940 have capacitors with very high working voltage ratings of 350VDC or so. Modern circuits and their capacitors, including those made post WW2 will have more normal ratings of 150 volts or so.
Surge ratings were dropped when solid state circuitry became the norm. Solid state rectifiers and power supplies did not go crazy when first turned on unless something had failed.
Thanks Ray. Do you think installing the modern 160V rated capacitors is too much of a risk in this case?
I think I get it now. WV is the expected maximum voltage that the capacitor will be expected to work at normally. Secretly, those old capacitors could sustain a higher voltage for a short period to accommodate power supply start up making that the 'real' rating. But to avoid confusing everyone, the manufacturers settled on the term 'working voltage' to state the rating during 'regular' service. Since modern equipment no longer has this startup problem with high voltages, components are no longer rated with that in mind and now the 'real' rating is printed on the capacitor and that should be considered a hard upper limit. I'd have to guess that the manufacturers still incorporate a lot of head room in these ratings or their component failure rate will be too high and sales would be impacted.
It is probably OK. I doubt that this is so old that the caps are of the reserve type and the draw of the tubes requires a ton of power. That transformer is pretty small. I'd worry more if there was an output amp putting out a watt or more.
You can check it by measuring the rectifier voltage when it is first powered on with the caps in place. If it is below 160 you would be OK. If it goes above I would go with 200v or 250v caps.
I would expect things to stay OK with 160v caps, especially if they are higher MFD than the originals. The time it takes for the caps to charge should keep things down till the tubes start conducting.
White, brown, gold, gold...9.1 ohm 5% carbon composition resistor. First gold band is 0.1 multiplier. Colors looked fine to me. Look for 9.1 ohm resistor in battery circuit.
Yep.
Your iso-transformer should have an own fuse. And with any overload on the secondary side of the iso-trans the fuse on the primary side should and must break the current. Your home fuse should not be envolved. If it reacts, your installation has an error somewhere.
But you live in danger. Really. You have a cable, where on one side is the main plug and on the other side are two crocodiles. I hope for you, you will never never be confused and work with this cable.
Yes that crocodile cable is risky to use. Wait until you see how I use it in the next video. Putting a fuse in the secondary of my isolation transformer strikes me as a good idea. I can never know, until it's too late, if shorting the isolation transformer secondary will draw enough to open the house circuit breaker. If not, something is liable to burn up including my house. If I were to leave my shop even briefly and that short circuit/fire scenario started, I might find my bench on fire and my house full of poison smoke in a minute. Now I'm motivated. Thanks for making me think about this a little further.