Aleph J illustrated build guide

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#10,301
Hai guys
I have an offer for Keithley 2015/2015P THD Multimeter for 130$
The manual is here Keithley 2015 benchtop MM and THD meter
Its a 20 y old model .

Some features and spec I copied from manual

  1. DCV measurements from 0.1μV to 1000V and ACV measure-ments from 0.1μV to 750V RMS, 1000V peak.
  2. The Model 2015 can make DCI measurements from 10nA to 3A and ACI measurements from1μAm to 3A RMS
  3. The Model 2015 can make 2-wire and 4-wire resistance measurements from 100μΩ to120MΩ.
  4. With a Model 2015, you can measure the forward voltage drop of general-purpose diodes andthe zener voltage of zener diodes.
  5. The Model 2015 can make distortion measurements from 0.002% to 100% (-94dB to 0dB).The 2015 uses a digital signal processor (DSP) to perform a fast Fourier transform on the signal applied to the front or rear voltage inputs. It then analyzes the levels of the harmonics present in the signal to calculate THD, THD+noise, and SINAD.
  6. The Model 2015 has a 10Hz-20kHz (60Hz default) two-channel function generator. It can be
    used to evaluate amplifiers, filters or other devices, or can be connected to the 2015 inputs. The
    function generator has selectable output impedances of 50Ω, 600Ω, and HIZ (50Ω default), and
    is unbalanced (coaxial). Its amplitude is 0-2Vrms for 50Ω and 600Ω (0.5Vrms default), and
    0-4Vrms for HIZ (1.0Vrms default).
  7. and many more like frequency spectrum analysis etc


How much useful can this be for doing some in depth DIY work

Can any member can share the experience
 
#10,302
Ok folks, work has calmed down and I am back to trying to debug the amp. I finally put my scope onto the amp and this explains some of what I am seeing. This is the gate of Q4. I am not seeing any oscillation anywhere else in the amp. Somehow just the gate is oscillating ??? I desoldered Q4 and R15. With those two removed I was able to confirm all the resistors in the bias circuit are correct. I also measured an hfe of 150 for Q4. I am at a loss. The only thing I can think of is to replace the pot with a fixed resistor, replace Q4, but that seems unlikely to work.
IMG_1137.jpeg
 
#10,303
Starting build on another Aleph J. I have the deluxe 5U chassis. The DIYAudio store uses the Schurter 4304.4045 filtered PEM in their back panel kit. Is the filtering component necessary? This PEM is $60 and is out of stock at Mouser. The non filtered PEM, 4304.6765, is $15 and is in stock. Would this one be just fine given the filtering in the power supply?
 
#10,311
Well I thought this build would be flawless. Hah! Tested just the power supply (universal power supply) with dim bulb tester and multi-meter. All fine. Hooked up amp boards (both) and dim bulb tester came on and stayed on; no change in brightness. This is not OK, right? Should dim some. Disconnected the amp boards and tested again. Bulb came on and then went off. LEDS lit; no smoke or heat. Did it again and the bulb didn't come on at all. Waited for the caps to discharge; tried it again. Same result. Picture below. Ideas and next steps?

1747855400866.jpeg
 
#10,313
With new builds do not power up both channels at once. Power up with only one channel connected, proceed following instructions, and only power up the second channel when the first channel is fully functional. If corrections need to be made on the first channel, check the second channel for errors and make the necessary corrections before powering it up.
 
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