Hi all - I recently recapped a Phase Linear DRS250. It powers up, and drives speakers at low levels, but when the volume goes up to even moderate levels it distorts badly. It sounds a bit like clipping, but the clipping indicator doesn't light up. Any guesses what could cause this?
Hello!
Do you have an oscilloscope?
Seeing the waveforms can help a lot to troubleshoot.
Do you have an oscilloscope?
Seeing the waveforms can help a lot to troubleshoot.
Thanks for the quick reply. Unfortunately, I don't have access to a scope, but if necessary, I could hire someone to scope it.
Sure, if you like to play with audio amps, scope is a must and you are going to learn a lot with this tool.
Where you live, you can buy starting at US$169.00 in Amazon - I can see several Hantek models.
I use a similar model that costs US$259.00 just rebranded in my country. Is more than enough for audio.
Where you live, you can buy starting at US$169.00 in Amazon - I can see several Hantek models.
I use a similar model that costs US$259.00 just rebranded in my country. Is more than enough for audio.
It sounds a bit similar to when powerful output transistors don't work. So, you have only pre-output middle-power transistors running. Somebody calls them drivers.
So, check if output transistors have power, check fuzes, etc.
The friend that gave it to me said that it worked the last time it was hooked. I don't have the service manual.
I did put my multimeter probes on it those outputs prior to posting, and measured ~ 52V. Not sure what's normal for those.
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Once you can do that, you can be assisted by people remote from you.
Digital oscilloscopes operate differently than normal analogue models. DSOs can lie to you. See if you can find a 100 MHz dual trace scope, take your time. Don't shoot for the moon. Later you can buy a DSO if you need the things they will do specifically. But you'll keep your analogue scope.
I have a ** very ** expensive MSO, and analogue scopes do things better. By expensive, I mean a significant portion of a new car. So if that digital scope isn't better than an analogue scope, what does that tell you about the cheaper DSO models?
Get a good meter. A bench meter, 5 1/2 digit maybe if you can swing it. AC frequency response up to at least 50 KHz. A used HP 34401A is very hard to beat.
Digital oscilloscopes operate differently than normal analogue models. DSOs can lie to you. See if you can find a 100 MHz dual trace scope, take your time. Don't shoot for the moon. Later you can buy a DSO if you need the things they will do specifically. But you'll keep your analogue scope.
I have a ** very ** expensive MSO, and analogue scopes do things better. By expensive, I mean a significant portion of a new car. So if that digital scope isn't better than an analogue scope, what does that tell you about the cheaper DSO models?
Get a good meter. A bench meter, 5 1/2 digit maybe if you can swing it. AC frequency response up to at least 50 KHz. A used HP 34401A is very hard to beat.
Here's the scope manual. Lots of good info there to get you started.
Hi knotscott,
I'm not sure about what you feel like, but whenever I get new-to-me equipment, I clean it up. Pop the knobs and us a toothbrush on it. Not too much fluid, don't let it run anywhere. The bezel will come off so you can clean the scope face area. Once you're done it should look much better.
This is also a great way to discover small broken things. You might want to blow the chassis out as well. Make sure it works first.
I'm not sure about what you feel like, but whenever I get new-to-me equipment, I clean it up. Pop the knobs and us a toothbrush on it. Not too much fluid, don't let it run anywhere. The bezel will come off so you can clean the scope face area. Once you're done it should look much better.
This is also a great way to discover small broken things. You might want to blow the chassis out as well. Make sure it works first.
Oh wow....thanks gents! DRS250 service manual ordered! I still have some homework to do, but have had a very good 24 hours!
It's about time I learned to use one of these things. Do I need a signal generator for it, or does it contain everything I need to scope the amp?
It's about time I learned to use one of these things. Do I need a signal generator for it, or does it contain everything I need to scope the amp?
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Yes, you will need some sort of sine wave signal generator - hardware or software like REW, etc. on a PC.
The scope only has a "CAL Terminal" which outputs a fixed 2 V peak-to-peak square wave at a fixed 1 kHz frequency.
This is used for the compensation adjustment of the scope probes and it's not very useful as an amp test signal.
The scope only has a "CAL Terminal" which outputs a fixed 2 V peak-to-peak square wave at a fixed 1 kHz frequency.
This is used for the compensation adjustment of the scope probes and it's not very useful as an amp test signal.
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An old smartphone with analog phone output (or your current) can serve as a signal generator - there are lots of audio generator apps.