Hi NareshBrd,
Well, the tuner pack may well be fine. They rarely fail so on that I'd have to disagree with what you are saying.
There are separate circuits for controlling the tuner between AM and FM where faults actually do occur. I outlined some of them earlier. But it is far too early to suggest replacement of anything given what we actually know. It is also too early to recommend throwing it out. We simply do not know enough about anything.
Well, the tuner pack may well be fine. They rarely fail so on that I'd have to disagree with what you are saying.
There are separate circuits for controlling the tuner between AM and FM where faults actually do occur. I outlined some of them earlier. But it is far too early to suggest replacement of anything given what we actually know. It is also too early to recommend throwing it out. We simply do not know enough about anything.
Hi NareshBrd,
I'm thinking of going with LM1875T or LM1876T chips. I wanted to remain with discrete output transistors, but the new driver chips compared to these complete amplifier chips make it not worth the effort. This application is lower power, lower voltages so chips may well be extremely reliable.
I am very familiar with using the uPc1225H driver chips, so I wanted to go with the tried and true, known option. I don't like that I have to use a totally different product.
I'm thinking of going with LM1875T or LM1876T chips. I wanted to remain with discrete output transistors, but the new driver chips compared to these complete amplifier chips make it not worth the effort. This application is lower power, lower voltages so chips may well be extremely reliable.
I am very familiar with using the uPc1225H driver chips, so I wanted to go with the tried and true, known option. I don't like that I have to use a totally different product.
The uPc chips were rated at +/- 36 V, on the high side.
The LM 1875 will take +/- 32 V, so you are close enough, and they are TI, no QC issues.
I was thinking which chip amps can be used at those supply rails.
The tuner has some sort of control chip, and the tuner is electronic, either capacitor or otherwise synthesized.
Not for DIY people to attempt a repair.
So the owner has to decide what is to be done, either send it in to an experienced service center, or otherwise deal with the situation.
The LM 1875 will take +/- 32 V, so you are close enough, and they are TI, no QC issues.
I was thinking which chip amps can be used at those supply rails.
The tuner has some sort of control chip, and the tuner is electronic, either capacitor or otherwise synthesized.
Not for DIY people to attempt a repair.
So the owner has to decide what is to be done, either send it in to an experienced service center, or otherwise deal with the situation.
Hi NareshBrd,
I have low supply voltages, no problem. The original driver chips Marantz used were not great. Early days in the semi industry for driver chips. uPc1225H would have been perfect!
The tuner does have a control chip, but if some measurements can be made I can point him in the right direction. I have offered to look at it if he's close.
-Chris
I have low supply voltages, no problem. The original driver chips Marantz used were not great. Early days in the semi industry for driver chips. uPc1225H would have been perfect!
The tuner does have a control chip, but if some measurements can be made I can point him in the right direction. I have offered to look at it if he's close.
-Chris
I saw that offer, the OP has gone quiet.
Close enough, Montreal, no idea about shipping costs.
It happens sometimes, the person posting the query decides to change his mind.
Close enough, Montreal, no idea about shipping costs.
It happens sometimes, the person posting the query decides to change his mind.
Yup, but my offer is open. I hope to save what isn't a bad tuner.
Older stuff is actually better than most new stuff. Performance is sometimes better, and it is definitely made better. If he's going to pitch it, I would love to repair it for myself. I have the matching preamp and even a GFA-1A amplifier that needs repair. An idiot serviced it. Anyway, why not?
Older stuff is actually better than most new stuff. Performance is sometimes better, and it is definitely made better. If he's going to pitch it, I would love to repair it for myself. I have the matching preamp and even a GFA-1A amplifier that needs repair. An idiot serviced it. Anyway, why not?
You could try a PM or telephone call, make him an offer?
You have worked on those, sometimes the units were not so well made, because like you said, early days for the semiconductor industry.
I expect a linear supply, and fairly good material inside, the same parts would have been used by other makes as well.
Adcom is not well known here, most of the audio stuff here was locally made (import restrictions), and a lot of people brought their sets home with them from their jobs abroad.
Japanese sets were popular, US and European, not so much. Few US sets were for our 220V, and many died due to line voltage fluctuation...
The Japanese sets worked and thrived here.
Very rare to see Denon and their ilk, most were mid range in price and quality.
That said, it was generous of you to make the offer.
Wait and see.
You have worked on those, sometimes the units were not so well made, because like you said, early days for the semiconductor industry.
I expect a linear supply, and fairly good material inside, the same parts would have been used by other makes as well.
Adcom is not well known here, most of the audio stuff here was locally made (import restrictions), and a lot of people brought their sets home with them from their jobs abroad.
Japanese sets were popular, US and European, not so much. Few US sets were for our 220V, and many died due to line voltage fluctuation...
The Japanese sets worked and thrived here.
Very rare to see Denon and their ilk, most were mid range in price and quality.
That said, it was generous of you to make the offer.
Wait and see.
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Well, I want to help him repair it mostly. I hadn't thought of ending up with it.
Yes, I have. I had a very large, 6,000 sq ft service shop for 16 years and we serviced mostly high end brands. Adcom wasn't bad. Better than.most in fact. I did see just about every brand available in North America and Europe.
You are correct in how these were made.
AC power is very tightly and well controlled in North America - most places anyway. Switchable 120 - 220 VAC power supplies were made unpopular as UL and CSA would not approve them. Certification bodies are overcautious idiots trying to protect unqualified people from getting a shock. It just increased unit cost. Then CSA decided to lower the temperature of the thermal fuse in transformers (another stupid move being overcautious) that cost the industry and consumers millions, if not more. Also increasing the cost to Canadian consumers. Besides, even an old transformer without thermal fuses could overheat. They stink and smoke a lot, but do not support a flame. So there was never a need to mandate a low temperature chemical fuse. The US and Canadian units that died failed because the thermal fuse opened I bet.
We shall see.
Yes, I have. I had a very large, 6,000 sq ft service shop for 16 years and we serviced mostly high end brands. Adcom wasn't bad. Better than.most in fact. I did see just about every brand available in North America and Europe.
You are correct in how these were made.
AC power is very tightly and well controlled in North America - most places anyway. Switchable 120 - 220 VAC power supplies were made unpopular as UL and CSA would not approve them. Certification bodies are overcautious idiots trying to protect unqualified people from getting a shock. It just increased unit cost. Then CSA decided to lower the temperature of the thermal fuse in transformers (another stupid move being overcautious) that cost the industry and consumers millions, if not more. Also increasing the cost to Canadian consumers. Besides, even an old transformer without thermal fuses could overheat. They stink and smoke a lot, but do not support a flame. So there was never a need to mandate a low temperature chemical fuse. The US and Canadian units that died failed because the thermal fuse opened I bet.
We shall see.
Hi Soundtec,
I'm glad it was a bad IC and you found it. Often this is not the case.
Yes, you can absolutely throw things way out when modifying a tuner. You have no idea! I see it on the bench all the time. Even CD players that no longer read a disc. Besides, just because something works does not mean it works properly!
When you don't know exactly how things work, everything seems easy and simple. Well, they are to me and other trained folks. Another truth, real technicians who are any good do not make youtube videos. You know why? Because they are too busy, and because the amount of background training needed is extreme.
People who are very good at what they do don't decide to just do it. It takes years of training and education and a natural aptitude for the subject. So whenever someone tells you something is easy (maybe that one thing is), they generally have little understanding of the subject. And again, just because something functions doesn't mean it functions well.
I do feel your comments are incorrect. Changing an IC will certainly affect the adjustments in that area of the circuit. That is the entire reason adjustments are included in the design. Even the MPX IC circuit will need alignment if you change it. IF amplifiers can be worse, but ceramic filters remove alignment for mediocre performance. By the way, they should be matched and performance can be improved. I have the equipment and jig for that. In the RF section, everything matters - a lot!
However you got that information - your source is dead wrong. Think about that.
-Chris
I'm glad it was a bad IC and you found it. Often this is not the case.
Yes, you can absolutely throw things way out when modifying a tuner. You have no idea! I see it on the bench all the time. Even CD players that no longer read a disc. Besides, just because something works does not mean it works properly!
When you don't know exactly how things work, everything seems easy and simple. Well, they are to me and other trained folks. Another truth, real technicians who are any good do not make youtube videos. You know why? Because they are too busy, and because the amount of background training needed is extreme.
People who are very good at what they do don't decide to just do it. It takes years of training and education and a natural aptitude for the subject. So whenever someone tells you something is easy (maybe that one thing is), they generally have little understanding of the subject. And again, just because something functions doesn't mean it functions well.
I do feel your comments are incorrect. Changing an IC will certainly affect the adjustments in that area of the circuit. That is the entire reason adjustments are included in the design. Even the MPX IC circuit will need alignment if you change it. IF amplifiers can be worse, but ceramic filters remove alignment for mediocre performance. By the way, they should be matched and performance can be improved. I have the equipment and jig for that. In the RF section, everything matters - a lot!
However you got that information - your source is dead wrong. Think about that.
-Chris
