Search results

My first Fluke was a 75 in the early 80's when I was dirt poor. It served it's purpose. Then the 87 came out. It became the standard at my day job. We've bought more than a 500 over the years. Some of the advanced features of the 289 are good for industry. Given the price, I can't see any...

The random order of the data taken, and lack of consistency makes it very difficult to make any determinations. At this point I don't even recall what the issue is.

Were all of the readings made with the meter on diode range or resistance?

There's nothing wrong with using a cheap function generator for checkout. Sine wave distortion will likely be 1% or more. If you have a scope play with the square wave genrator and watch what happens at the frequency extremes.

mine was ...function generator.

I got caught in a pinch and needed some kind of a sine wave generator to see if an amp would pass a signal. I found it on itunes for free. I like the Waveteks but own all HP. Bought them all at Dayton hamventions 20-30 years ago. I got to work on the 204C oscillator last year when it had a...

This amp being designed with budget in mind only has 2 transistors in the front end vs 4 for 400/700. They saved the cost of a transistor and used diodes for the bias circuit which was a bad move. The schematic is hard to read as apparently there was a paper shortage so everything was crammed...

Here's the manual. Read the section on stability and thermal run away and the service bulletin. Ask yourself if it's worth it.

Hard to beat that price. There are some cracks for some of these scopes that xtend the badwidth etc. The downside of them is the trace is a joke compared to a decent analog scope. In that I mean the trace is so fat you miss high frequency oscillations riding on the waveform. I have a 50 year...

Although I can't confirm this story, I seem to recall Cerwin Vega used to claim their sub could be plugged into the wall. Assuming an 8 ohm load and 120 volts at the outlet that would calculate to 1800 watts and 15 amps which would not blow a breaker.

Getting this amp to work is going to be a valuable learning tool with minimal cost except for labor. A successful WOPL does not yield any troubleshooting experience. Referring to the blown speakers, one time a rock n roll band brought in a JBL 15" to get reconed. During the show, the voice...

The .6 volts across the diodes is good. Has Q6 been tested? I think it would be best to make a table with columns for both channels and write down the readings one at a time for both channels. For the time being skip Q1-Q5 and associated diodes because those transistors affect offset which is...

with power off,and fuses pulled, check eveything in circuit and compare readings with known good channel. Prefer to use diode scale.

Hopefully my attempt at humor in the previous post was understood. You can't gain much by reading voltages on a direct coupled amplfier which is where the P/L's fall. One stage drives the next and they all appear out of whack. Put a meter on the diode scale and compare readings on each...

Having worked in the power electronics business for more than 40 years there is one thing that has become readily apparent. I've learned that manufacturers know noting about their product. The longer they are in business, the less they know. Consequently, a person should never read the...

I believe the 2nd and 4th heatsink is the negative DC leg for each channel. In quasi comp systems it is critical that the RCA 410 is used, as opposed to an MJ15024/21196 to prevent oscillations. I learned the hard way that using the same transistor for driver and outputs leads to oscillations...

No, theyre on the outputs. Color is brown-black-black.

I use BNC-binding post connectors on my scope and cables with dual bananna jacks. Download a signal generator on your phone. Inject a sine wave from the signal generator into the amp and look at it with the scope. Verify the level is nearly the same at 20HZ, 1khz and 20Khz. If the level...

The few 4000's I've worked on must have averaged 100 cracked solder joints on the mother board. That's why I won't touch them now.