grundig: 8050; Musikschrank
Hi all....I hope your summer is going well. I am working on this radio, and need to change the electroletics . Is there an easier way....the output transformer is directly on top of connections. I have to remove it and connections to get to it. Also...does anyone know where I can get phono cartridge for this set? thanks AL
This is what happened. The set was playing on BC. Poor sound quality...not much amplification. The electro can heated up and started leaking . I shut her down. Disconnected can, Replaced the 2 100uf caps. Now tubes light....but complete silence on all bands. I am used to American ac/dc radio repair....Where should I start to trouble shoot? Any help appreciated.....Thanks AL
I think you have at first to carry out a "rough limitation" of the faulty area, that means faulty power supply or defective AF- or RF-stage/s.
- As far as I understood, you replaced the electrolytic capacitor/s 2x100 µF ("electro can"). But what is the matter with the rectifier ? Is it still working in spite of a possible temporarily overload caused by the leaking current through the defective capacitor ? Value of the positive voltage at plus terminal ?
- Did you measure the supply voltages (e. g. plate voltages at pin5/ EL 95 and the voltage drop at the cathode resistor 200 Ohms/pins 2/EL 95 ?
You see, we need much more information from you to support your trouble shooting ...
Thanks for help Rolf.......Just to be sure...my voltages are taken from chassis ...and I am looking for AC voltage? AL
- I meant in case of DC the voltages between chassis/ground and the resp. test points (e. g. pin 5 of EL 95, see schematic). This requires that the negative lead of your instrument is always connected to the chassis/ground.
- For AC voltage you have to measure directly between the two pins of the rectifier input or, alternatively, between the transformer's secondary output winding terminals (without any ground connection).
Be careful and good luck !
Hi....Between _ and + of rectifier I am getting 450v ac. On pin 5 of EL95 I get 400v dc....on pin 2 of EL95 where 200ohm resistor is I get less than 1v.....anything stand out? thanks AL
Hi...My meter was in need of fresh battery. The correct voltages are: 280v ac between neg and pos of rectifier...260v dc at pin 5 of EL95....and still less that 1 volt at pin2 of 200ohm resistor on EL95
Alfred, sorry for the delay, but I have a lot of trouble in the company.
A voltage drop of only 1 V at the 200 Ohm common cathode resistor is much too less. Please check at first if this resistor has the correct value. Second the 100 µF capacitor may be faulty (short-circuit). Third, check the grid 1 resistors 1,8 Mohm / 1 kOhm and 18 kOhm / 47 kOhm of the EL 95s and, additionally, replace both 10 nF capacitors between the plates of the ECC 83 and the grids 1 of the EL 95. And the correct ground/chassis connections of the grid- and of the cathode resistors are very important, please check this also.
Thanks Rolf.......I checked all resistors ( all in range) 100uf electro checks good....all grounds..good. The only thing left that you suggested is the 10nf caps. Would they be equal to .1 mfd? .01?
...1nF=1 000pF, and 1µF=1 000nF...
...the US has been very slow to recognize the nF (nanofarad), where it has been used in Europe for years...
Thank you, Todd, for your information.
I think, in the next step Alfred should disconnect both 10 nF from the ECC 83 plates and measure the voltage at the screen grids pins 6 of the EL 95s. Please include a check of the 600 Ohm/2Watt preresistor. Voltage value should be in the range of 246 V to 229 V as stated in the schematic .
Thanks for info! I disconnected caps from pin 1 and 6 plates of ecc83. The voltage at pin 6 of EL95s is less than 2 volts. Does this lead us to problem? thanks AL
...after checking my Q-score ;>), downloaded the schematic to see what's going on...
...you should be measuring 8,8/9.8 volts at EL95 pin 2 (cathode). Those 10nF (.01) caps from the ECC83 plates to the EL95 g1s are probably leaky; try measuring the voltage on the EL95 g1 (pin 1 or 7). If that voltage is substantially positive, the caps need replacing (plate voltage from the ECC83 is leaking through onto the g1 of the EL95, cutting it off). If they are ERO paper caps, they should be replaced anyway...for whatever reason, the ERO paper caps have apparently been particularly troublesome after this many years...
...also, as Rolf mentioned, is that 100µF cathode bypass cap (from EL95 pin 2 to ground, across the 200 ohm cathode resistor) OK? (Unfortunately, these earlier Grundig schematics don't give us reference designators to help point out the parts we're talking about...it would be easier if we could be talking about something like 'C705' instead of trying to describe what and where the cap is...)
...there is a 600 ohm 2 watt resistor between the positive sides of the two 100µF filter capacitors that you replaced. It feeds the screen grids at pin 6 of the EL95s. Is that open? Is it properly connected to pin 6?
...your rectifier output goes directly to one 100µF filter. That provides your plate voltage for the EL95s through the output transformer primary winding. Then there is the 600 ohm 2 watt resistor, and then the other 100µF filter capacitor. That should go directly to pin 6 of both EL95s, and also branch out to the rest of the chassis (the plate voltages for most of the other tubes are also derived from this source). If that 600 ohm resistor is open, or misconnected, nothing in your set is going to function...
Thanks Todd.....The 600 ohm 2 watt resistor checks ok ( 590ohms) . I will replace the 2 10nf caps. The 100uf filter that goes to 200ohm resistor is seperate from the can. It checks good, but I will replace that too. This is very frustrating because the set was working ( poorly, but working on BC) She starting leaking juice from electro can, I shut it down...cut connections from old can....installed 2 100uf 450v caps mounted on top of chassis....and now all tubes light..along with dial lights....but I can't get a buzz out of her! I will work on it more tonite.....thanks AL
As Todd mentioned, a missing supply voltage after the the 600 Ohm / 2 Watt resistor would cause not only a malfunction of the power output tubes due to too low screen grid voltage but would be also the reason that all other stages do not work.
Therefore my question again, Alfred: If there is indeed a voltage of approx. 280 V at plus of the rectifier resp. the first 100 µF capacitor, only a short circuit after the 600 Ohm resistor could be the reason for a screen grid voltage (pin 6 EL 95s) resp. supply voltage for the other stages of only 2 volts as you measured. Therefore you should now disconnect each wire which leads to the pre-stages from this resistor so that only the screen grids of the ELs 95 are supplied. In case the 600 Ohm resistor is definitely not defective you should measure then a voltage of more than 229 Volts at the screen grids pin 6. Can you give us information about this item ?
...with all respect to Rolf, I don't think you have a short after that 600 ohm resistor. If you did, with 280 volts going through it directly to ground, it would certainly be a 'crispy critter', or at the very least smoking profusely when you try to run the set. Try measuring the DC voltage on both ends of the resistor, and double-check your wiring. If you're seeing 280 volts at both ends of that 600 ohm resistor, but only 2 volts on EL95 g2 (pin 6), and the resistor is not going up in smoke, then that would suggest something is not connected correctly; trace the wiring back from EL95 pin 6 and make sure it's connected to your second 100µF 450V cap and the resistor...also, try measuring plate voltages on some of the other tubes (look at EBF 89, pin 6 or ECH 81, pin 6, for example; 232 volts or 246 volts, respectively)...
...incidentally, the lights and tube filaments are going to work no matter what; they run off a different power transformer winding (completely independent circuit)...
Thanks guys....Lets make sure we are on the same page. I am getting 280v AC with meter probes on neg to pos as written on rectifier. Then 260v AC on other side of 600 ohm resistor . My voltages that are low, are taken from chassis to pin 6 or 2 of EL95 DC. And the negative marking on the rectifier is not to chassis........Am I doing this correctly? If not guide me through please....thanks AL
...the AC measurement was intended to check if the high voltage winding of your power transformer is OK. That needed to be done on the two input terminals of the rectifier, probably marked '~'. All the other measurements are DC voltages, including the + and - terminals of the rectifier and the resistor. The - terminal of the rectifier does go to ground; it connects to the low side of the filament winding which is grounded. And all of that is connected to the chassis. Unlike the AC-DC radios you're used to, this one does not have a 'hot' chassis since it uses a power transformer (built-in line isolation). So for all your DC voltage readings, you should have the negative lead of your meter connected right to the chassis.
...one other thing: You said the old electrolytic can started heating up and leaking; there could be a short in the rectifier (although that would, in most but not all cases, blow the fuse). If you have an internal short in the rectifier, it will place unrectified AC onto those 100µF 450V caps, which will try to pass it directly to ground. That will cause them to overheat; next time you try to work on this, check and see if your new electrolytics are getting hot, especially the first one coming right off the rectifier. If your new caps are getting hot, you'll need to completely disconnect the rectifier and check it for shorts with an ohmmeter...
Ok...I think I understand now. The electo that is going through the 600ohm resistor is showing 252 volts dc on other side of resistor. The electro that is connected direct to pin 6 is showing less than 2 volts. Voltage at pin 6 is less than 2 volts. Where is the 252 volts going? According to schematic it is going to pin 6 also. Note; When I do an ohms check from 600 ohm resistor to pin 6, I get condenser action. Shouldn't I get 0 ohms? I am going up North for a few days ( near you Todd) Portsmouth NH. I will pick this up next week ( Tuesday) Thanks for all your help.....AL
...yes, you should get zero ohms from EL 95 pin 6 to one end of the 600 ohm resistor. I'm beginning to suspect you have that resistor wired wrong, and that 252 volts isn't going anywhere. The resistor is supposed to be connected between the positive leads of the two 100µF 450V caps.
Here is a redrawing of the rectifier, filter caps, and resistor the way they should be wired (with a little help from Microsoft Visio 2003). Maybe this will be a little easier to decipher...
Note that the resistor is connected between the two 100µF filters. The pink wire off the first cap feeds the plates of the EL 95s through the output transformer primary winding and should measure 261V DC at the + lead of the first cap. The 600 ohm resistor connects the two caps together and feeds the rest of the radio, including the g2 (screen) grids of the EL 95s, with the second 100µF filter providing extra filtering. This point (the + lead of the second cap) should measure 246V, along with EL 95 pin 6. One wire off this second cap goes to EL95 pin 6, and the other wire proceeds into the rest of the chassis, its first stop being a 220k resistor on ECC 83 pin 6.
- defective resistor due to overload for which the reason must be found out and which could have been the possibly damaged/leaky old 100 µF (remember Alfred's first post !).
- So we have no reason for the missing supply voltage 246 V (229 V) at the screen grids unless a wrong measurement was made or
- a mistake during re-wiring/replacement.
Rolf and Todd, thank you for your terrific diagrams! From the first 100uf positive to one side of 600ohm resistor, I get 0 ohms. BUT....From the second 100uf positive to other end of 600ohm resistor I have no connection. It goes directly to pin 6 of EL 95.....SO...I put a jumper wire connecting 100uf to 600ohm resistor, AND SHE IS WORKING! If you remember my first post, I was having problem getting to electro can connections, because the output transformer covered most of it. I am thinking, when I disconnected leeds from can, I could have accidently clipped a wire from electro to resistor? I will furthur diagnos working conditions of set and inform. Thanks AL
On BC Radio plays well ( sometimes the volume goes up and down on its own) FM signal is weak, even on a strong FM station. The Eye tube does not illuminate...and no movement inside. Is the eye supposed to work on BC and FM? Thanks AL
That should work on any band, although it will work differently on FM. The eye tube is an EM34, octal base. This set has a 6.3 volt parallel filament string, so you could have an open filament on the eye tube and it won't affect the other tubes. Can you see if you have a lit filament? Also, check for DC voltages on pins 3, 5 and 6, and open 1 meg resistors on pins 3 and 6...
...you still probably have other paper caps in there that should be replaced (it sounds like you've only worked on the audio output area so far). They could be causing some of these problems. Also, there is a 10µF electrolytic shown in the FM detector circuit; if it's bad, that could help explain the weak FM. And the band switches in these radios are notorious for developing flaky contacts...and just as notorious for being difficult to get to to clean them...
...you have taken a quantum leap on the degree of difficulty scale from AA5s to German radios...;>)
...but patience and perseverence will be richly rewarded once you get this working properly...
While working on FM tonite, I discovered adjustment screw on top of metal square can covering the FM tuner. When that screw is connected to the can ( which I did accidently with screw driver) FM works loud and clear.....How should I proceed? Thanks AL
in the first place it would be very helpful if you could make some pictures from the tuner . At least I myself have no other information about your radio than the small photo (ID 135579 /John Hupse) from the back side of the chassis and the schematic. And what do you call "can" ? The enclosure of the electrolytic capacitor ? All of this is not sufficient to answer your question. Next you should mark the respective screw and publish the marked photo/s here in the RM.
By the way - I would prefer the more systematic approach like Todd advised you in his Post No 25 ...
Best regards Rolf
Hi...The can is the metal enclosure around the FM tuner. I will take some pictures. I can't find the 10uf electro that Todd mentioned in the Fm circuit. I changed all paper caps.The strongest FM station is coming in weakly even with dipole antenna hooked up. Thanks AL
...that electrolytic is not in the FM tuner. It's all the way at the other end of the FM signal chain, in the detector circuit (around the EABC 80 tube). It may have nothing to do with the problem you're describing in the tuner; it would more likely cause distortion of the sound on FM.
As they've been saying over at ARF, you may need to look at the cathodes (pins 3 and 8; pin 3 especially) of the ECC 85 for an open cathode resistor or coil. Many of these FM tuners used wire-wound resistors (typically 150-180 ohms) returning the cathodes to ground, and those did have a tendency to open up. However, as I pointed out, this particular FM tuner is shown as using coils (RF chokes?) instead of resistors to return the cathodes to ground. Those 'coils' could in fact be wire-wound resistors, although they typically used a different symbol for wire-wound resistors and labelled them with a resistance value. One of those could conceivably have opened up, or have a cold solder joint, perhaps...may require somehow getting inside that metal enclosure to take a better look...at the very least, as they advised at ARF, you can try taking a resistance measurement from pin 3 or pin 8 of the ECC 85 socket to ground. You should see a very low resistance (approximately 150 ohms if there is indeed a wire-wound resistor there, or near zero ohms if there are only coils).
Thanks Todd....I am getting less than 1 ohm from pin 3 and 8 to chassis. There are coils ,not resistors as schematic shows. AL
On the ECC85 Plate 1 I am only getting 2 volts. On pin 6 I am getting 125volts. According to schematic I should be getting 152volts on pin 1 ? Thanks AL
...yes, you should be seeing 151V on pin 1. According to the schematic, the plate (pin 1) is fed through a 68k 1W resistor, then three coils. You need to check for any opens, especially in that resistor. Tracing that through does not look easy by the looks of your pictures; it's hard to see where the tube socket is. Is that large gray resistor 68k? See if it's open. There's a 4.7nF (.0047µF) cap to ground on the other side of that resistor. If the resistor is open, check that cap for a short (especially if it's a paper cap). Also check for continuity from pin 1 of the ECC 85 socket to that resistor to see if one of those coils is open.
Thanks Todd....That large grey resistor is 11.5k ohms...so its probably the one on the other side( 12k) I will look for 68k resistor....Is the tubular symbol with line through it denote 1 watt? There aren't any paper caps in this area...I will look for corresponding 4.7nf.....thanks AL
...that's a 6.8k 1 watt resistor you need to look for, not a 68k. Yes, the single line across the resistor symbol represents 1 watt. That 12k is also 1 watt, and it's OK, since you have the proper plate voltage at pin 6. I would expect that 6.8k to be another similar large grey resistor in there somewhere, but I can't find one in any of your pictures.
...studying the pictures, I do see one coil that looks suspicious. It's at the bottom of your first picture (DVC00111,JPG). To the right it connects to what looks to me like a red polystyrene cap, and it looks like there is another cap right underneath the red one. Is that red cap 140pF? And what is the other cap underneath it? At any rate, that coil looks like something has happened to it and the wire on it is all over the place. Check if that's open...maybe something you could rewind if it is...
Hi Todd...I have been out of town a few days. The 6.8k 1 watt resistor is underneath chassis it reads 7.4k, it is attached to FM coil can? ( looks like IF can) . That coil you talk about in picture checks good with ohm-meter . I am trying to figure out what cap is with that resistor (6.8k) It is very difficult working with this chassis upside down (as you know!) While I was away, I received the phono cartridge I ordered in the mail...and that is working perfectly. So now all is left is our FM problem. I will try to get some numbers off those caps you mentioned.........Thanks AL
The poly cap under the red one is 2000pf. The red one I can't read, but its 500v. That 6.8k resistor gets mighty hot! Question? From pin 1 of ECC85 to chassis, I should be getting condenser action, right? I am getting 35 ohms....even when I put a new cap over that section. I cant find the 4.7nf cap! AL
OK...I found the 4.7 cap....It looks like a resistor, its the long brownish cap in the upper left hand side of first pic. Should I replace it/ and with what value .005? AL
OK. My bad. You have a short on that B+ line for all intents and purposes, not an open. That 4.7nF is a tubular ceramic cap. To replace it, .0047 or .005µF should be OK; make sure it's rated at 500 or 630V. It's a bypass cap, so the value is not critical, or even type for that matter (you could probably use a film-type cap here), but since it's on a B+ line you need to use a healthy voltage rating. What you can do first is disconnect one end of the cap and put your ohmmeter across it. If it measures 35 ohms, it's the bad one. (You won't see 'capacitor action' on a cap of that value; it should read open.) The only other candidate for that kind of leakage is a 15pF cap shown between a 100 ohm resistor coming off ECC 85 pin 1 and one section of the FM tuning gang. It is rare, but not unheard of, for a cap of that low value developing that kind of leakage; check that one as above if the 4.7nF doesn't pan out...
Hi Todd......We are on to something! The 4.7 cap is marked 4.7nk and has a black band ( ground?) I clipped a .005 630v non- polorized cap in its place. I am now getting 144v on pin1 of ECC85. How ever, I am getting a loud squeal along with loud static. A station can be heard through back ground noise. Before I do anything else, I wanted to check with you........Thanks AL
PS The squeal and static is controled with volume control ( if this means anything?)
You got your B+ back and some signs of life. Seems like I've read somewhere that occasionally those tubular ceramic caps developed some sort of silver migration problem that caused them to become leaky like that. They are not polarized as such; they are marked like the old paper caps to indicate which lead is connected to the outer electrode. The squeal and noise you are now reporting is something that I don't think I've encountered before, but it sounds now like something is oscillating that shouldn't be. The clip leads that you used to temporarily connect a replacement capacitor could actually be causing this. (At FM frequencies, there is enough inductance in those leads that they could be creating an unwanted feedback loop into some part of the tuner and causing oscillation.) Now that you have determined that that 4.7nF cap was your problem, get rid of the clip leads and solder in the replacement, making sure you keep the leads as short as you can. See if that helps...
I soldered cap in place with very short leads, and she was still squealing. I adjusted one of the screws in the FM section, and she is now playing good! Not great...the sound quality is a bit basey ( as if not fully tuned) but she is loud as ever. I think its as good as its going to get. One more minor problem....It is very difficult to replace the bulb for the ferrite antenna light. In trying to do so, I cracked the bulb. It is a small 6v lamp ( smaller than 47 or 51 type) Do you know where I might get one? And is there a service book that instructs how to replace? Todd...Thank you for all your help in this restoration! Thanks to Rolf also, for getting me in the right direction! Al
I'm glad that problems could be solved via this thread. That is the main thing - but can somebody tell me why this sits on model 5079Ph?
I was wondering about the high number of posts in this thread - and then also clicked the link to the model - which is Grundig 5079PH instead on one of the models Grundig 8050 Musikschrank!
Is there any reason for this or should the article be moved to Musikschrank 8050 or to Musikschrank 8050WE or has the right model (export to USA?) to be created first?
Hi Ernst....It should be under 8050. I dont know how it wondered to 5079ph....thanks AL
...I had no idea it was even there...I had been replying directly under the Forum title and didn't go to the model page...
...by the way, Al: is this a US model? (Easy to tell by looking at the FM dial: does it go to 108 or stop at 100?) If so, you could submit it as a new model if a US version doesn't already exist...
...on second thought, if it's called 'Musikschrank', it probably isn't (a US version would have had the 'Grundig-Majestic' label on it, would have English nomenclature on the controls, and would probably have a label on the back calling it 'Musical Instrument 5080' or something like that)...
It is in fact model 8050/USA Made in Chicago by Majestic.
Can you please give me some details? I will then delete all posts after no. 43 so we have a straight forward thread. Maybe somebody even tells me which posts are unnecessary to read for the future - or does a summary we can get a better picture? I did not study it, for lacking the time.
Here I would be glad to have the tube line up and number. Perhaps you can send me a picture of the plate or sticker plus one of the scale only? Please give also the other units like record changer and/or tape recorder.
After the model is up you then can load your other pictures (front, chassis, back, scale etc.).
Thank you for your cooperation. I had sent you an eMail but had no answer yet on that - well , it is short since ...
Tube line up ECH81 EC92 ECC83 EBF89 EAA91 EL95 (2) ECC85 EM34/35
PERPTUUM EBNER REX TURNTABLE MARKED 4A ON BOTTOM PE10 CARTRIDGE
Please let me know if any more info is needed....ALAttachments:
Thank you for your data. With this I could bring in the new model and move the thread to it.
You could now load up your pictures to the model.
Please have a look if measurement and other data is really corresponding with your model.
I hope that somebody will shorten this thread to what is necessary when this is done.
This the the 6-7v 0.1 amp bulb needed for ferrite rod antenna indicator. Some one suggested it might have been used in some older Volkswagon auto's. Anyone have it in their bulb box?? thanks ALAttachments:
- Grundig 8050USA (57 KB)
- Grundig Lamp BA7s (26 KB)
RS Components, www.rs-components.com/, still handles BA7s lamps. The RS internal code for the 6V, 200mA type is 339-3298.
Best regards, Emilio