Popular parts distributors for Germany include Reichelt, Farnell, Mouser, Digikey. For radial electrolytics, Panasonic FC is a good series. Not sure how much faith you can put in axials these days, should you need any of those.
Be warned that you have a bit of a learning curve ahead of you if you have barely gotten your first multimeter now (I started out with one much like this, but that's been like 15 years). You'll probably need to watch a few multimeter tutorials, as well as learn some general electronics troubleshooting techniques that would allow you to pinpoint the source of your problems and find potentially faulty parts. Oh yeah, and you need a decent soldering iron with a few different tips, some traditional leaded 60/40 solder (or even eutectic if you want to get fancy) and some sort of flux as well.
A few (audio) repair related YT channels off the top of my head:
12voltvids
xraytonyb
EEVBlog
Dr Cassette
I may have forgotten some. The likes of Louis Rossmann and FFcossag are probably too much focused on modern-day surface mount stuff but are worth a look.
Be warned that you have a bit of a learning curve ahead of you if you have barely gotten your first multimeter now (I started out with one much like this, but that's been like 15 years). You'll probably need to watch a few multimeter tutorials, as well as learn some general electronics troubleshooting techniques that would allow you to pinpoint the source of your problems and find potentially faulty parts. Oh yeah, and you need a decent soldering iron with a few different tips, some traditional leaded 60/40 solder (or even eutectic if you want to get fancy) and some sort of flux as well.
A few (audio) repair related YT channels off the top of my head:
12voltvids
xraytonyb
EEVBlog
Dr Cassette
I may have forgotten some. The likes of Louis Rossmann and FFcossag are probably too much focused on modern-day surface mount stuff but are worth a look.
There are Panasonic FC 47uf/50V... EEU-FC1H470. I personally prefer Panasonic FR.
The things you will want to use in selecting replacement parts are:
1) lead spacing (distance between the pins). Should be the same as the original for good fit
2) diameter (ensure it will fit)
3) voltage - at least what the original was; higher is OK, lower isn’t
4) I almost always use 105 deg C rated caps (which the FC, FR etc. are)
The things you will want to use in selecting replacement parts are:
1) lead spacing (distance between the pins). Should be the same as the original for good fit
2) diameter (ensure it will fit)
3) voltage - at least what the original was; higher is OK, lower isn’t
4) I almost always use 105 deg C rated caps (which the FC, FR etc. are)
That small 'lytics nowadays are smaller physically and have much thinner, bendable leads as the ancient Roederstein's. So most probably any modern cap of appropriate capacitance and voltage rating will fit onto the PCB.
But will replacing all 'lytics solve the OP's issue of a far too high output offset voltage, unless the one in the NFB leg is shorted?
Best regards!
But will replacing all 'lytics solve the OP's issue of a far too high output offset voltage, unless the one in the NFB leg is shorted?
Best regards!
I tried to swap the transistors from the right channel with the transistors from the board that it was firstly in the device (has problem with the left channel, the right is working good). Still the excessive voltage is there.
Also tried to swap the four smaller capacitors on the right channel, two red, one blue and one axial, but either with no success. The excessive voltage on the right channel is still there.
Any advice anybody, what should I do next?
I swapped the ones that are missing on the picture.
Also tried to swap the four smaller capacitors on the right channel, two red, one blue and one axial, but either with no success. The excessive voltage on the right channel is still there.
Any advice anybody, what should I do next?
I swapped the ones that are missing on the picture.
The excessive voltage on the right channel was caused by one (or more) of these transistors.
I replaced almost all electrolytic capacitors, all power output transistors with new, and still the excessive voltage on the right cnannel was present. So i started replacing everything from the other board i have, a few components at a time and i test the output voltage, replacing the four transistors at the picture above solved the excessive voltage and now everything works fine, no problems with sound or temperature. Matching replacement power output transistors are BD901 and BD902.
I will do a full recap of the system, but i would like to ask a few questions about replacing the caps.
- The two big capacitors on the power amplifier board (2 x 10.000uf 30V), for replacement closest values i found we're 10.000uf 35V, should i go with these caps or maybe higher like for example 12.000uf 50V? Also the originals have 4 connectors and the replacements only two, will they fit? On the picture below the four connectors are in the blue circle, only two are used.
- On the power amplifier board there is one orange Siemens capacitor like on the picture below with values 1000uf 40v and is pretty hard to find and pretty expensive, is it necessary to replace?
- Also on the power supply the big capacitor on the picture below is pretty hard to find and on a one or two places i found it is the same NOS Made in West Germany. Should i change it?
- On the tone control board there are 19 axial capacitors (15 2,2uf 63v and 4 1uf 100v) i like to replace. Which ones should i use, will it make any difference in the sound?
1uf 100v:
Link 1:
Link 2:
The price of the first is 1.70€ for the second 0.25€. There are around 10 caps of this value in the system.
2,2uf 63v
Link 1:
Link 2:
Link 3:
Greetings.
EDIT: What a bad luck, a minute after posting and the right channel emits a random loud pop sound. It was doing this before the defect appeared, since the repair i used the system 3 days all through the day and there was no problem till now. Any opinions what could cause this?
I replaced almost all electrolytic capacitors, all power output transistors with new, and still the excessive voltage on the right cnannel was present. So i started replacing everything from the other board i have, a few components at a time and i test the output voltage, replacing the four transistors at the picture above solved the excessive voltage and now everything works fine, no problems with sound or temperature. Matching replacement power output transistors are BD901 and BD902.
I will do a full recap of the system, but i would like to ask a few questions about replacing the caps.
- The two big capacitors on the power amplifier board (2 x 10.000uf 30V), for replacement closest values i found we're 10.000uf 35V, should i go with these caps or maybe higher like for example 12.000uf 50V? Also the originals have 4 connectors and the replacements only two, will they fit? On the picture below the four connectors are in the blue circle, only two are used.
- On the power amplifier board there is one orange Siemens capacitor like on the picture below with values 1000uf 40v and is pretty hard to find and pretty expensive, is it necessary to replace?
- Also on the power supply the big capacitor on the picture below is pretty hard to find and on a one or two places i found it is the same NOS Made in West Germany. Should i change it?
- On the tone control board there are 19 axial capacitors (15 2,2uf 63v and 4 1uf 100v) i like to replace. Which ones should i use, will it make any difference in the sound?
1uf 100v:
Link 1:
Link 2:
The price of the first is 1.70€ for the second 0.25€. There are around 10 caps of this value in the system.
2,2uf 63v
Link 1:
Link 2:
Link 3:
Greetings.
EDIT: What a bad luck, a minute after posting and the right channel emits a random loud pop sound. It was doing this before the defect appeared, since the repair i used the system 3 days all through the day and there was no problem till now. Any opinions what could cause this?
Last edited:
More often than not, that's a bad solder joint. They are not uncommon in equipment this old, and some even elude detailed visual inspection. (Techs will even perform wholesale resoldering in some cases.) Obviously it could also be another faulty component, but I'd start with the basic stuff. After the solder joints, I would give the trim pots a good look, the Piher pots Grundig used have a tendency to corrode and even fall apart. You can get those new still.
Usually ESR is a decent indicator of electrolytic capacitor health (unless it's dead short, of course). ESR testers are not entirely cheap but handy to have around, and the good thing is that caps can usually be tested in place (assuming they are well discharged), even if it's not a dedicated "in circuit" tester.
Thanks for the post and sorry for my late response. Since i'm not experienced in troubleshooting i thought maybe it would be best to replace all components in the power amplifier board as it may be more damaged components since the board was defective maybe one defective component have damaged others too. But i can't find the complete replacement parts list for this model, i have the online version of the service manual but the replacement parts list is not complete. I've searched to buy a printed version there are a few but i'm not sure if it will have a full parts replacement list. Anybody familiar with the service manuals does they originally provide the full replacement parts list? I have changed all electrolytic capacitors and the main transistors. Next largest number of components are resistors in a few different types and sizes, what i'm not sure of is the wattage of each and how to measure them. There is a method with measuring their physical size but are let's say 1/4 watt resistors all equal in physical size?
Greetings.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.