It's weird that they didn't use Matsushita relays exclusively. I mean, Technics is Panasonic is Matsushita. They mostly used their own made components throughout, because they really did make everything.
I think it was evident in the build of the G50 vs the earlier IC powered Technics, which were much better made. If they had used their own relay, there would not be a problem, as they relays in the older Technics are fine, never had an issue with mine
You may not be aware that these AA, AAA, New class A etc. Technics models are all a bit weak on loading and don't suffer 4 ohm or lower impedance speakers well. Mine auto-switches the transformer secondary windings for 4 ohms but the labels on the speakers often lie because speaker ratings are not consistent. The amplifiers will work but not as hard as you would expect with more output power, without stressing the output stage, heatsinking and power supply.
Technics had moved on from being a premium hifi brand to a mainstream manufacturer of affordable, general audio products by the time this model arrived. It showed in many ways as they moved into new and lower budget markets, the music industry and general consumer audio. I have an earlier SU-V50 that is called class AAA (still similar to class S, after A. Sandman) and looks well appointed inside, with PCBs chock-full of discrete components and a fancy thermal wick heatsink. It would have cost a lot more to produce than SU-G50. I've never compared the sound quality but it's quite possible the older amp. was no better for having discrete parts.
I've read a few complaints about the relays in later Technics models but having survived their expected 10 year life span, it still doesn't surprise that poor audio connectors like relays have become a problem after >25 years. Just aerobic contamination is enough to spoil relay contact.
Technics had moved on from being a premium hifi brand to a mainstream manufacturer of affordable, general audio products by the time this model arrived. It showed in many ways as they moved into new and lower budget markets, the music industry and general consumer audio. I have an earlier SU-V50 that is called class AAA (still similar to class S, after A. Sandman) and looks well appointed inside, with PCBs chock-full of discrete components and a fancy thermal wick heatsink. It would have cost a lot more to produce than SU-G50. I've never compared the sound quality but it's quite possible the older amp. was no better for having discrete parts.
I've read a few complaints about the relays in later Technics models but having survived their expected 10 year life span, it still doesn't surprise that poor audio connectors like relays have become a problem after >25 years. Just aerobic contamination is enough to spoil relay contact.
Hi Ian,
I think the DEC is finished, the sound was quite then the amp went silent. I will be getting that new relay. I guess the cut out sound is the relays fault as i had to give it a few taps to get it working both channels this time.
I have 2 IC amplifers, i do remmeber running the G50 a few years back in 4ohm speakers, even though the back said 8ohm. I try to find which of my speakers are best, unfortunately they are all 8ohm.
The Celestion Sl-6 - way too low sensitivity 82db
However Technics SB-6 and Coral CX5 are 90db and 93db.
Yes Technics bought out many affordable cd players etc. That is a nice amp your SU-V50, that is the heatpipe sort of thing my SU-V4X has. The poor G50 certainly didnt get a good heatsink like that. Only good thing in the G50 is the IC. I was going to use the spare V4X relay ( being from 1984), maybe is best to go new, as its pain to have to take the whole board out all the time, the new relay should be good for 10 years I think.
I think the DEC is finished, the sound was quite then the amp went silent. I will be getting that new relay. I guess the cut out sound is the relays fault as i had to give it a few taps to get it working both channels this time.
I have 2 IC amplifers, i do remmeber running the G50 a few years back in 4ohm speakers, even though the back said 8ohm. I try to find which of my speakers are best, unfortunately they are all 8ohm.
The Celestion Sl-6 - way too low sensitivity 82db
However Technics SB-6 and Coral CX5 are 90db and 93db.
Yes Technics bought out many affordable cd players etc. That is a nice amp your SU-V50, that is the heatpipe sort of thing my SU-V4X has. The poor G50 certainly didnt get a good heatsink like that. Only good thing in the G50 is the IC. I was going to use the spare V4X relay ( being from 1984), maybe is best to go new, as its pain to have to take the whole board out all the time, the new relay should be good for 10 years I think.
Uh...perhaps I wasn't clear enough.
P.S
If interested, you can measure the DC resistance of the bass driver at least, by just using a ohmmeter on the terminals. Typically, this will measure 6.5-7R for an 8R system and 3.2 for a 4R. There will be exceptions but that's what I read on the hundreds of domestic speakers I've checked in many years of repairing and recycling them.
i.e. 8 ohms is fine, 4 ohms is not so fine and if your speakers are all 8 ohm, that should be fine too, excepting any that prove to have rubbery specs, which is what I'm getting at because it's a problem with modern HT speakers rated 6 ohms but prove to be lower. It's marketing because low impedance speakers will sound louder and clearer, therefore to average consumers, must be better too 🙄
P.S
If interested, you can measure the DC resistance of the bass driver at least, by just using a ohmmeter on the terminals. Typically, this will measure 6.5-7R for an 8R system and 3.2 for a 4R. There will be exceptions but that's what I read on the hundreds of domestic speakers I've checked in many years of repairing and recycling them.
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Hi Ian,
update : I fitted the new relay. The other day, i turned it up a bit and heard a click and then the sound went? I thought it was the CD player since it was modded?
Could it be the relay or something else with amp? currently playing cd player, so far so good?
I got the TE Relay - nice fit bit smaller than the tall DEC.
Cool, so i can measure DC current on a speaker driver?
update : I fitted the new relay. The other day, i turned it up a bit and heard a click and then the sound went? I thought it was the CD player since it was modded?
Could it be the relay or something else with amp? currently playing cd player, so far so good?
I got the TE Relay - nice fit bit smaller than the tall DEC.
Cool, so i can measure DC current on a speaker driver?
Technics amps usually have rather advanced protection circuits. It either clicked away the amp due to high DC offset, or due to overheating of the output stage. If it happens again, measure DC voltage at the relay contacts (that connect to the output stage).
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Hi Welcome thanks 🙂
It was playing fine, i went to turn it down and felt the top of the amp and it cut out again 🙁
I did the same mod that was on the other G50 with speaker wires at the relay output. Do i measure from there? difficult since the G50 does not have access to underneath or the transistors on the heatsink?
I have an old 1984 Technics SU-V4X spare relay ? i could use but its old 1984, but is a matsushita part.
? not enough thermal compound on ic? heatsink is warmish to the touch but not hot, but maybe normal, even though today is coolish and rainy (winter here)
It was playing fine, i went to turn it down and felt the top of the amp and it cut out again 🙁
I did the same mod that was on the other G50 with speaker wires at the relay output. Do i measure from there? difficult since the G50 does not have access to underneath or the transistors on the heatsink?
I have an old 1984 Technics SU-V4X spare relay ? i could use but its old 1984, but is a matsushita part.
? not enough thermal compound on ic? heatsink is warmish to the touch but not hot, but maybe normal, even though today is coolish and rainy (winter here)
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The relay is switched off by the protection circuits, as it should be when there is a fault detected and they are working correctly. As welcome wrote, you should check for any significant DC present at the relay (amplifier side) contacts. With a schematic, we might see there are other components that also connect to the amplifier outputs which will be just as good as contact points for taking measurements.
Think about the requirement there - don't just blindly follow instructions. For example, those coils are in series with the outputs and scraping a small amount of enamel from the wire at a through-hole will provide a contact point for measument from the top, if it's all too hard to perform measurements below the board. If you do remove the board again, don't forget to trace out the circuit from Chip to relay, so that you know what parts could be used next time - and there probably will be a next time for any true OCD DIY tinkers 😀)
Think about the requirement there - don't just blindly follow instructions. For example, those coils are in series with the outputs and scraping a small amount of enamel from the wire at a through-hole will provide a contact point for measument from the top, if it's all too hard to perform measurements below the board. If you do remove the board again, don't forget to trace out the circuit from Chip to relay, so that you know what parts could be used next time - and there probably will be a next time for any true OCD DIY tinkers 😀)
Hi Ian 😀 Thanks for the reply, yes OCD ADHD DIY tinker like me 😀 There is good news i have part of the schematic for the G50. I can see the relay, which points to check ? It would earth an dc measurement and the pin to get the reading.
Great the new relay is fine as its a pain to put the amp together again. I will be careful I dont want any pops or bands ! haha I aready expereinced a cap blowing in a cd player mod, wrong way around .
Great the new relay is fine as its a pain to put the amp together again. I will be careful I dont want any pops or bands ! haha I aready expereinced a cap blowing in a cd player mod, wrong way around .
An externally hosted image should be here but it was not working when we last tested it.
Hopefully there won't be any pops or bangs if you are taking a careful note of what you see on inspection and check it for voltages on the schematic, such as it is, when there is an opportunity.
The solid heavy lines indicate the principal signal path. Conventionally, just the left channel is shown this way for clarity. As you can see, there are 2 opamp symbols shown in the power module IC601 and the left channel output is at pin 3 (nominally 0V) which connects to coil L601/R609 parallel combination. If you locate R609 or its right channel counterpart, they will have bare leads so you can use either end of the resistor as the output test point for measuring any DC "offset" between speaker ground and amplifier output. Other components also connected there could be used if more convenient - use common sense.
When you measure the DC status of amplifiers, make sure speakers and inputs are disconnected or volume is right down so that you measure under fully quiescent conditions (no signal, no load). Anything smaller than +/- 50 mV DC will be acceptable but you might expect a little less, say <30mV before signing off on it.
The solid heavy lines indicate the principal signal path. Conventionally, just the left channel is shown this way for clarity. As you can see, there are 2 opamp symbols shown in the power module IC601 and the left channel output is at pin 3 (nominally 0V) which connects to coil L601/R609 parallel combination. If you locate R609 or its right channel counterpart, they will have bare leads so you can use either end of the resistor as the output test point for measuring any DC "offset" between speaker ground and amplifier output. Other components also connected there could be used if more convenient - use common sense.
When you measure the DC status of amplifiers, make sure speakers and inputs are disconnected or volume is right down so that you measure under fully quiescent conditions (no signal, no load). Anything smaller than +/- 50 mV DC will be acceptable but you might expect a little less, say <30mV before signing off on it.
Hi Ian 🙂
Thanks for the help.
I was thinking I would put the ground probe on the earth terminal, so i can concentrate on not touching the pins on the IC. I will locate this R609 to see what i get there for a reading.
I would do these readings once the amp is in protection mode or when i power it up? with volume down without anything attached to the amp?
Thanks for the help.
I was thinking I would put the ground probe on the earth terminal, so i can concentrate on not touching the pins on the IC. I will locate this R609 to see what i get there for a reading.
I would do these readings once the amp is in protection mode or when i power it up? with volume down without anything attached to the amp?
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