Brief Introduction
Being un-well for over a year really does give one a different view of life, does it not? So instead of yet another project and being obsessive, embrace what I have. Back in 2012, bought a legless compact (basically upright) Telefunken console. Ups (German equivalent to oops) apparently decided to do destructive testing on it, so replaced it with a local Delmonico 981 with Körting chassis 24651 from the original owner's son, who was chuffed someone wanted to enjoy it as intended (rather then decoration as he had). I have some paperwork, missing the schematic, plus a postcard in what might be a Slavic language on the turntable (hole punched through) and have a receipt from 1975 for a replacement transformer and a EZ81 valve (still new in the box), the latter two in my view, combined moving it from Chicago to Phoenix, means really loved it, cabinet seems to confirm (except the side facing the hall got the children's toys and a melted spot in the top). All those years ago didn't know better so used it without replacing the electrolytic capacitors, had a terrible hum when switched on a florescent lamp, glad didn't blow the EZ81; also needs an alignment but without instructions, embrace as is. My understanding is: Delmonico bought components from different manufacture's and inserted into cabinets manufactured in house (which I suspect reduce cost via reducing shipping cost). Not only is it unique having valve rectification in May 1964 (well past the selenium rectifier becoming common), audio is simply a pair of ECL86s.
By the way, a dear friend far from me, will be making a new hardwood plywood cabinet per original dimensions, then somehow getting it back to me, so she is not totally destroyed and the chassis will inhabit a far superior cabinet (original was pressboard and literally crumbling besides the breaks). Then, if still alive and able, not only electronically restore, improve the KW reception (fun pulling in distant stations and enjoying them) and add the UW stereo converter/demodulator.
Audio Amplifier
The resistors are all 5 percent carbon composition so suggests a higher quality build per my understanding. Interesting most have held their value, except those 100KΩ and above, and those remaining close to value are basically bang on. Instead of building the PCL86 mono blocks, in part because the eBay listing never mentioned an odd circuit design (HT to the screen of the pentode) and have DC filament supply, which greatly adds to the cost, gain a ECL86/PCL86 amplifier by electronically restoring the one in the console and adding unfiltered DIN inputs (only has for phonograph and tape) and if want to go further, can connect external speakers. Still sorting out costs, not decided if go 1 percent or 0,1 percent, of course thin film Vishay. For now, keeping the original film capacitors, a few Ero Fil IIs, unbranded styrenes, and unbranded resin dipped cylindrical (suspect polyester which well are non-linear), as first want to hear the sound with the waxies replaced with Panasonic PPs, then decide on the remaining capacitors should be changed to WIMA MK10s (MK4s are for low frequency as smear the treble if remembering the right way around).
Desire to Have a Rudimentary Understanding of Induction and RF Circuitry
After a number of hours of research, I come away with an understanding it is often necessary to have non-inductive resistors in RF. Being there is no schematic available (spent countless amount of time looking), unable to ask if such information is required. My personality then tries unsuccessfully to find if inductance is in the wire, radiated, or both, plus, what it looks like (ex. AC looks like a sine wave). Anyone know of a resource?
Thankfully found a source for carbon composition, I was going mad with hours and hours and hours of research trying to find non-inductive resistors in the high values needing replacing. See what I mean about obsessive? Ah the joys of being an INTJ. 😆
Well, I desire to keep this post short, done trimming it, so better sign off before decide to add more.
Being un-well for over a year really does give one a different view of life, does it not? So instead of yet another project and being obsessive, embrace what I have. Back in 2012, bought a legless compact (basically upright) Telefunken console. Ups (German equivalent to oops) apparently decided to do destructive testing on it, so replaced it with a local Delmonico 981 with Körting chassis 24651 from the original owner's son, who was chuffed someone wanted to enjoy it as intended (rather then decoration as he had). I have some paperwork, missing the schematic, plus a postcard in what might be a Slavic language on the turntable (hole punched through) and have a receipt from 1975 for a replacement transformer and a EZ81 valve (still new in the box), the latter two in my view, combined moving it from Chicago to Phoenix, means really loved it, cabinet seems to confirm (except the side facing the hall got the children's toys and a melted spot in the top). All those years ago didn't know better so used it without replacing the electrolytic capacitors, had a terrible hum when switched on a florescent lamp, glad didn't blow the EZ81; also needs an alignment but without instructions, embrace as is. My understanding is: Delmonico bought components from different manufacture's and inserted into cabinets manufactured in house (which I suspect reduce cost via reducing shipping cost). Not only is it unique having valve rectification in May 1964 (well past the selenium rectifier becoming common), audio is simply a pair of ECL86s.
By the way, a dear friend far from me, will be making a new hardwood plywood cabinet per original dimensions, then somehow getting it back to me, so she is not totally destroyed and the chassis will inhabit a far superior cabinet (original was pressboard and literally crumbling besides the breaks). Then, if still alive and able, not only electronically restore, improve the KW reception (fun pulling in distant stations and enjoying them) and add the UW stereo converter/demodulator.
Audio Amplifier
The resistors are all 5 percent carbon composition so suggests a higher quality build per my understanding. Interesting most have held their value, except those 100KΩ and above, and those remaining close to value are basically bang on. Instead of building the PCL86 mono blocks, in part because the eBay listing never mentioned an odd circuit design (HT to the screen of the pentode) and have DC filament supply, which greatly adds to the cost, gain a ECL86/PCL86 amplifier by electronically restoring the one in the console and adding unfiltered DIN inputs (only has for phonograph and tape) and if want to go further, can connect external speakers. Still sorting out costs, not decided if go 1 percent or 0,1 percent, of course thin film Vishay. For now, keeping the original film capacitors, a few Ero Fil IIs, unbranded styrenes, and unbranded resin dipped cylindrical (suspect polyester which well are non-linear), as first want to hear the sound with the waxies replaced with Panasonic PPs, then decide on the remaining capacitors should be changed to WIMA MK10s (MK4s are for low frequency as smear the treble if remembering the right way around).
Desire to Have a Rudimentary Understanding of Induction and RF Circuitry
After a number of hours of research, I come away with an understanding it is often necessary to have non-inductive resistors in RF. Being there is no schematic available (spent countless amount of time looking), unable to ask if such information is required. My personality then tries unsuccessfully to find if inductance is in the wire, radiated, or both, plus, what it looks like (ex. AC looks like a sine wave). Anyone know of a resource?
Thankfully found a source for carbon composition, I was going mad with hours and hours and hours of research trying to find non-inductive resistors in the high values needing replacing. See what I mean about obsessive? Ah the joys of being an INTJ. 😆
Well, I desire to keep this post short, done trimming it, so better sign off before decide to add more.
Yes, photos will help much. Anyway, there's no need for sure to use 0.1 % resistors. Maybe there's even no need to replace the original ones.
Are these capacitors ERO Fol's instead of ERO Fil's? I suspect so.
And yes, I'd also replace the expensive ECL86's by still cheap PCL86's and adapt the heater supply.
Best regards!
Are these capacitors ERO Fol's instead of ERO Fil's? I suspect so.
And yes, I'd also replace the expensive ECL86's by still cheap PCL86's and adapt the heater supply.
Best regards!
Check out the Radiomuseum entry for Delmonico 981. The schematic is a different chassis but it should be pretty similar to yours. https://www.radiomuseum.org/r/korting_koerting_delmonico_981_24611.html
At first glance it looks to be a standard stereo German tube radio from early '60, a schematic is not really required if you know this kind of radio, the difficult part to restore is usually oxidation at piano keys selectors and some detuning of the radio frequency section. I would not go overboard on the audio amplifier restoration because the output transformers aren't usually of the best quality so you will get limitations both at high and low frequencies, and the routing of the signal around the complex switching matrix of the source selector will pick-up some background noise. There are better chassis of that era, from Saba and Telefunken as example, but this one should still be very enjoyable after the restoration. ECL86 are still easily available here so I personally would not replace them. They may also still be working fine, the amplifier of this kind of radio was not putting them to the limit and they had a long life.
At first glance it looks to be a standard stereo German tube radio from early '60, a schematic is not really required if you know this kind of radio, the difficult part to restore is usually oxidation at piano keys selectors and some detuning of the radio frequency section. I would not go overboard on the audio amplifier restoration because the output transformers aren't usually of the best quality so you will get limitations both at high and low frequencies, and the routing of the signal around the complex switching matrix of the source selector will pick-up some background noise. There are better chassis of that era, from Saba and Telefunken as example, but this one should still be very enjoyable after the restoration. ECL86 are still easily available here so I personally would not replace them. They may also still be working fine, the amplifier of this kind of radio was not putting them to the limit and they had a long life.
I thought it be pointless if there was no interest, have a few took for the aforementioned friend. Plus, was not needed for the question.
Yes, there is a golden barrel cactus in my bedroom, only two south windows and the other has the industrial sewing machine in front of it. I love succulents, got a stag horn cholla in the front room, some folks think I am crazy, as if get stuck, gives you an intense burning sharp pain for a solid 20 minutes, even if the spine is not in your flesh. But the new spines are soft and feels interesting to touch.
Interestingly lists MB and UW (mono), not the KW, which does have.
Adjusted for inflation be about $95USD.
Surprisingly clean.
For fun, let's see if anyone can tell my handedness.
Replacement capacitor shorting to low impedance or ground of the original capacitor. Sometimes bigger is not better, sometimes not going to fit.
On the underside, on the switching, far from the transformer, found a resistor on one switch bent onto the next, shorting. Will get in there with Dad's jewelers pliers and straiten the leg. Would not surprise me if a factory oops was missed, after watching over 200 of Mr. Carlson's videos, he has shown worse factory oopses.
Polyester film?
Styrene film capacitors?
This puzzles me, the yellow lead is filter capacitor ground, goes to the negative end of the electrolytic, and the positive end is grounded to the chassis.
Yes, they are ERO Fol capacitors, memory failed me.
I assumed all would remember the recommendation to do the first build using already made circuit on PCBs and selecting PCL86 mono blocks, sorry about that.
Hopefully these ECL86s are still good, they are Telefunken. I don't have a tester yet, so if make sound, will keep using them until die or the tester shows up and they test week. See, it is not just heater voltage that would have to change, it is also the circuit, please see attached.
Are you saying all Körting receiver sections are the same? If so, why then the differences in valves, including an additional?
I do have a schematic which is the same or at least close (both channels have ECL86 output valves) for the audio amplifier.
We were looking for the receiver section schematic to address inductance of high value film resistors.
But I know nothing, this is my first electrical restoration of one.
I expect the receiver to need tuning, I have watched over 200 of Mr. Carlson's YouTube videos and have seen amazing results, even when the settings were factory. One reason I bought a Heathkit 7A.
So then what is a good percentage of matching resistors in each channel, 2 percent? Trouble is if go with 5 percent resistors, then have to buy multiples, even with the ten quantity discount, more then selecting a 0,1 percent and not having to match.
Interesting you mention Telefunken, I also had that feeling, especially seem to recall it having more receiver stages, and plan to go all out on that electrical restoration, why staring with this one, get some practice. Plus, the Körting be in the bedroom and eventually the Telefunken in the front room (leaning towards external speakers). Does the Telefunken have less to no background noise?
What I love to add to the Telefunken is FM stereo converter/multiplexer.
Easily available off eBay.de? I don't see many Telefunkens, certainly no pairs. But, I am not set on them and if found a great deal, get Philips or Valvo, put those in, and save the Telefunkens (EZ81 and ECH81 are also Telefunken, the ECC85 is a Siemens, EBF89 is a Valvo. By the way, trying to slowly accumulate spare valve, soon there will be a very limited supply and want to keep using these consoles for another 50 years, God willing I live to be 86.
Oh well! Please replace the 50+50 µF 350/385 V electrolytic filter capacitor due to it being dried out and all those capacitors with paper covers and wax ends as well. The mustard colored and the silvery shining capacitors most probably don't need to be replaced.
The 47 Ω resistor between the filter electrolytic's negative terminal to common ground serves to generate a negative voltage, most probably (I don't have the schematics handy) to bias the output tubes. Check that blue electrolytic in parallel with it also.
Last but not least carefully straighten the ECL86 pins.
Best regards!
The 47 Ω resistor between the filter electrolytic's negative terminal to common ground serves to generate a negative voltage, most probably (I don't have the schematics handy) to bias the output tubes. Check that blue electrolytic in parallel with it also.
Last but not least carefully straighten the ECL86 pins.
Best regards!
Kay, danke für die Hilfe! 😀
The paper and wax capacitors, some call waxies, will be replaced with Panasonic PP, as I did in the vintage Jensen speakers and found the sound pleasant. I am not convinced there is not diminishing returns on capacitors, plus, as someone said, this isn't worth going all out on.
After over 200 videos of Mr. Carlson, well aware of the danger of living leaky capacitors in. Speaking of danger, also be replacing the ceramic capacitors on the mains with XY rated (help prevent shock if ever fail).
I plan to replace only the out of value resistors, see no reason to replace them all with metal film, in fact, there is information out there saying the inductance of these can cause harm (unwanted oscillation) in RF circuits.
I say all this in hopes a misunderstanding will be removed.
I plan to replace all electrolytic capacitors, less than a dollar, then know everything is working as should and best chance for decent reception (I live a distance from the towers and the few stations are weak).
So for not seen any bent ones, rather, the sockets allow the valve to lean over if the valve is bumped.
What means by this?
As I said in the initial post, that is the plan. Showed it as thought interesting it is lifted off ground, not seen that before. I am also aware there is a 50μF limit (assume 5650μF is close enough) since valve rectified, wish knew the impedance of the power transformer to be sure that was also in specification, but sometimes need to let go of being anal and remind myself it worked for the PO for many years.
The paper and wax capacitors, some call waxies, will be replaced with Panasonic PP, as I did in the vintage Jensen speakers and found the sound pleasant. I am not convinced there is not diminishing returns on capacitors, plus, as someone said, this isn't worth going all out on.
After over 200 videos of Mr. Carlson, well aware of the danger of living leaky capacitors in. Speaking of danger, also be replacing the ceramic capacitors on the mains with XY rated (help prevent shock if ever fail).
I plan to replace only the out of value resistors, see no reason to replace them all with metal film, in fact, there is information out there saying the inductance of these can cause harm (unwanted oscillation) in RF circuits.
I say all this in hopes a misunderstanding will be removed.
I have attached a schematic which is close, same valves except the rectifier, have not checked all the component values, though layout looks the same, better than nothing. If so, now see the capacitor does look to be a negative supply.
I plan to replace all electrolytic capacitors, less than a dollar, then know everything is working as should and best chance for decent reception (I live a distance from the towers and the few stations are weak).
Any tips on this?
So for not seen any bent ones, rather, the sockets allow the valve to lean over if the valve is bumped.
Just thought there's a lot of work waiting for you 😉 .
On one of your pics both ECL86's appear to sit aslope in their sockets, which made me assume their pins may have been bent. But if this isn't the case, there's nothing to do on this, of course.
Btw, your schematics doesn't show that 47 Ω resistor with the 'lytic in parallel. Either the secondary's center tap and the filter 'lytics are grounded instead.
Best regards!
You are correct, the RF circuitry must not be disturbed. The carbon resistors are more suitable than some other types.
In hot running equipment, the internal heat keeps the resistors dried out, and on value.
Dave, good seeing you again. The ECH86 is a triode (usually the pre stage) and output pentode. So, this is the entire audio amplifier, very compact.
ECL86.
I am well familiar… had a good stash of them (and parts for a project) before the purge.
Are the OPTS under that PCB behind the tubes?
I disassembled 2 Kortings, 1 with ELL80, and the other with EL84. Often EL84 and ECL86 OPTs were interchangable.
dave
Dave, thought you meant output valves, not output transformers. Yes, also took me a second, they are on the underside.
Why would one disassemble a good vintage chassis? Are Körtings that bad?
Why would one disassemble a good vintage chassis? Are Körtings that bad?
Good seeing a familiar name. I know directed at Dave, though I can answer this, least can do for you: 35x50 and 40 tall.
Particularily the Europeanones, make really decen tparts for inexpensive amplifiers.
And i care little about the vintage bit These things had decent parts (tubes & iron), most of the rest is not worthy of saving unless you are a masochist.
dave
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Save any of the pots particularly for tone?
As for being a masochist, there is a lot of us. 😛 Most are far worse than me, collecting a plethora of them, as for me, I am satisfied with the two I have and don't have the energy or health to fix more than that. If the cabinet was not so fantastic on this one, pull the chassis and turn it into a tabletop, consoles, unless a compact like the Telefunken, take up a lot of space.