I don't plan on opening up the stereo amp, but I'd like to test it to make sure it's working within spec. I picked up the below listed handheld oscilloscope that I mainly use to adjust speed on a few cassette decks I repaired. Specs says it can take a 50v input. Can I send the amp a 1khz tone at a low volume and connect this scope to observe and compare both channels of high level outputs on the amp? I was already planning on using a fluke meter to measure DC offset on the outputs. Thanks!
AUKUYEE Updated 2.4" TFT Digital Oscilloscope Kit with Power Supply and BNC-Clip Cable Probe Q15001 (Assembled Finished Machine) https://a.co/d/5hOLb00
AUKUYEE Updated 2.4" TFT Digital Oscilloscope Kit with Power Supply and BNC-Clip Cable Probe Q15001 (Assembled Finished Machine) https://a.co/d/5hOLb00
It is rated for 50 volts PEAK...not RMS, so it's input voltage limit for a sine wave test signal would be around 35 volts...but if you test with music signals, which are not just sine waves, one would need to be careful there, maybe keep the audio test levels below about 20 volts or so.
Mike
Mike
Could buy a X10 probe to be safe
Input impedance is 1Mohm, so a standard one will be fine
Brian
Input impedance is 1Mohm, so a standard one will be fine
Brian
Thank you all for the advice!
I got the amp and started testing it. I measured 5mV DC offset on each speaker output. Before I connected any speakers or my oscilloscope I wanted to see what kind of voltage I'd get from the speaker outputs from playing a 1 kHz tone from my iPhone using a headphone/RCA plug which I've done successfully on other amps. Even with the volume turned up, I was only getting a few volts out of the speaker jacks. I then plugged up some sacrificial speakers and again even with the phone's volume maxed out, the tone and some music I played never got "loud" as you'd expect, and the bass was very weak. This was even in both channels. Now, I am an amateur, but I've heard of issues where an amp will "output voltage, but not current". Is that what this sounds like? Thanks again!
I got the amp and started testing it. I measured 5mV DC offset on each speaker output. Before I connected any speakers or my oscilloscope I wanted to see what kind of voltage I'd get from the speaker outputs from playing a 1 kHz tone from my iPhone using a headphone/RCA plug which I've done successfully on other amps. Even with the volume turned up, I was only getting a few volts out of the speaker jacks. I then plugged up some sacrificial speakers and again even with the phone's volume maxed out, the tone and some music I played never got "loud" as you'd expect, and the bass was very weak. This was even in both channels. Now, I am an amateur, but I've heard of issues where an amp will "output voltage, but not current". Is that what this sounds like? Thanks again!
Carver m-1.5t
Someone on the carver fb group said he had similar low output on his and a tech said it needed to have the two really huge caps in the ps replaced. They were shorted, according to him.
Someone on the carver fb group said he had similar low output on his and a tech said it needed to have the two really huge caps in the ps replaced. They were shorted, according to him.
That is weird. I'm going to run it through a kill-a-watt tonight to see what it draws. There is a company that refurbishes carver amps and they'll add a switch on the back that supposedly has circuitry to eliminate possible turn on thump. I have several of these little Belkin power switches. It's a little box you plug into the wall or surge protector or whatever and plug your device into it so you can turn the device on and off. Newer ones are controlled with Bluetooth or wifi with your phone. Progress!
A 10:1 probe is essential for many uses of a 'scope - the low capacitance allows probing most parts of a circuit without disturbing it. And it protects the 'scope by having 10Meg series resistance. Just be sure to select 10:1 and calibrate the probe for the 'scope.
Was just gonna come back here and say it's working! I've used my iPhone to drive amps before with no problem but someone said I should use an actual preamp. I used the preamp output from my Marantz avr and its works! Sounds good. No issues. Guess I got lucky. It appears this amp has never been worked on from the intact factory warranty sticker on the case. I'll listen to it for a while and decide if I want to upgrade the parts. Shouldn't be too much if I do the labor.
Anything is possible.
Anything is possible swapping part for part if I make a mistake. Most people just swap the 40 yr old caps.
Lol. Thanks. The extent of my "tinkering" would be to possibly replace 40 yr old caps after depleting them. I bought it to actually use/listen to 👍🏼
Carver was one of the brands I used check out when visiting my local hifi shop as a kid.
That scope is actually quite good and usable.
I bought one almost as a joke just because it was very cheap and I did not mind waiting a couple Months for the free shipping option, but was agreeably surprised.
I bought one almost as a joke just because it was very cheap and I did not mind waiting a couple Months for the free shipping option, but was agreeably surprised.
Many Carver amps are quite different from traditional. The differences lie primarily in the power supply and protection circuits. The protections circuits are quite effective and can shut down the power supply (actually idle it) which often leads to a technician diagnosing an amplifier fault as a power supply problem. This can be compounded if you set about testing the power supply without understanding how it works. But... you get used to it.
Over on thecarversite.com there is an extensive library of service manuals, one of which covers the M-1.5t. It's an excellent manual with an extensive theory of operation section the clarifies many things. The manual is available free after you join the site.
Over on thecarversite.com there is an extensive library of service manuals, one of which covers the M-1.5t. It's an excellent manual with an extensive theory of operation section the clarifies many things. The manual is available free after you join the site.
That's why in that case I still rely on my 1964 CRC OC344D single beam all tubes oscilloscope :
A French Navy surplus oscilloscope, which offer 50 volts per division, that is to say 400V peak-to-peak on the whole screen... A super fine trace, thanks to its 2kV post-acceleration.
T