9444B - alternate procedures for BIAS, LF, Current Limit?

The 9444B Service Manual calls for an oscilloscope, tone generator and distortion analyzer, unlike the 9444A which can be serviced with a multimeter. Basically, the fundamental stripped waveform from the distortion analyzer is sent to the scope and... analyzed. Are there alternate procedures for these adjustments? I have software oscope, tone generator and spectrum analyzer, the only thing I'm lacking is a distortion analyzer with output. My options:

1. Purchase a distortion analyzer - I was outbid on a HP 331A today.

2. Build one - http://sound.westhost.com/project52. htm

3. Call Ira - does he post here? If he doesn't, I'm hesitant to ask him for free advice.

4. Ask the smart people here for advice - Help!

This freeware might do the job: Low-Cost Audio Testing Techniques Using a PC | Suite101 .

A User Manual and the software can be downloaded from: http://audio.rightmark.org/download.shtml

Thanks mah, I RTFM and played with Rightmark, as far as I can tell it does not have the capability to output fundamental nulled distortion signals in realtime.

I was hoping that someone would know of a simpler method of making said adjustments, possibly with a multimeter. For example, the 9444A service manual shows no less than 5 methods of adjusting bias-the simplest is done powered off and only requires a screw driver!

FWIW Most service folk's are eager to help.Whether they can help you for free with advice (If you do the Work) or if you have to send it in to them for a fee..

If you can't find what you need I wouldn't hesitate to call Ira.He may have one of these simple solutions for you.

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Originally Posted by _88

.....For example, the 9444A service manual shows no less than 5 methods of adjusting bias-the simplest is done powered off and only requires a screw driver!

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Where did you get a 9444A service manual?

^ I found it online, it's missing a few pages, but it shows DC offset and the 5 ways to adjust bias :) I tried to attach it, but at over 2mb, it's too large :( Suggest me a hassle free way to upload it.

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Originally Posted by Altec Best

FWIW Most service folk's are eager to help.Whether they can help you for free with advice (If you do the Work) or if you have to send it in to them for a fee..

If you can't find what you need I wouldn't hesitate to call Ira.He may have one of these simple solutions for you.

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Thanks. I'll call Ira for free advice as a last resort.

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Originally Posted by _88

I tried to attach it, but at over 2mb, it's too large :( Suggest me a hassle free way to upload it.

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How about email ? I can send you my email through PM's and I'll upload it.. How many pages is it ?

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Originally Posted by Altec Best

How about email ? I can send you my email through PM's and I'll upload it.. How many pages is it ?

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I just looked at the 9444A pdf, it's 10 pages, the first 2 are cutsheet. Pages 1-6 are missing from the Operators Instructions. Page 11 is missing from the Service Instructions, which is most likely just the cover sheet if it's printed like the 9444B O&SI manual. I have pages 1-20 for the 9444B, which appears to be complete. I wish the pages were numbered 1 of 20, 20 of 20, then we would know for sure. PM me your email if still interested.

edit- just found 6 addendum pages for the 9444B and AP2600A

My progress:

Current Limiting - used the oscilloscope in Visual Analyzer. The test requires the amp be driven hard to check for asymmetrical clipping. Channel 1 clipped evenly, then 8 ohm 200 watt dummy load started making funny noises. I rechecked both channels with a 12 ohm 1100 watt hot plate (complete with tea kettle), both looked good. Now I get to build a proper water cooled 4 ohm load with water heater elements and repeat check by the book - yay!

LF cancel and bias - I think both can be checked with free software. The brainstorm:

SweepGen sine wave > sound card L out > amp/dummy load > voltage divider (100k lin pot) > sound L in > Spectrum Lab super-dooper notch filter > sound R out > sound R in > Visual Analyzer o'scope

Spectrum Lab allows for building custom filters - the bad news - it's been almost 20 yrs since I've fired up a C compiler. If I fail as a code jockey (highly likely), I'll probably build Rod Elliot's DA design posted above with only two filters - 60Hz and 1k.


Visual Analyzer - Visual Analyser 2011 XE

Spectrum Laboratory - DL4YHF's Audio Spectrum Analyser

SweepGen - Audio Tools - from David Taylor, Edinburgh

I was able to accomplish the service checks with the free software programs listed in my last post on Jan 20, 2013, which for some reason is still awaiting moderation. It took a bit of C programming and less than USD $10 of hardware. Since this forum seems somewhat link and attachment challenged, I'll post a full tutorial at a well known DIY audio forum with lots and lots of links, pics and large(?) attachments :)

PS- the 9444A and 9444B manuals were found at the Great Plains Audio website a few years ago. The last time I checked they were removed from the site.

Back again: Altec Amplifiers

Edit: No biasing details.

Look at the procedures in the service manual for the 9442A{listed at the above link). They may possibly be the same.

Thanks mah, that site has a much clearer 9444B schematic!

btw- I mailed the 9444A and B manuals to Altec Best, hopefully he has them sorted out.

edit- I may be mistaken about downloading the manuals from GPA, it was probably one of the free service manual sites. Regardless, both appear to have complete service sections.