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Grand Junction, Colorado |
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Grand Junction, Colorado |
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Noisy, Out of Balance Blower
My Alpha 87a served me faithfully for almost 4 years before I encountered the first problem. As time went by, I noticed that the blower that cools the final tubes - a pair of very expensive Eimac 3CX800A7 triodes - was becoming noisier, and even showing signs of being out of balance by imparting a vibration to the case.
Fortunately, the 87a was still under warranty. A call to the factory resulted in the technician offering to send me a replacement blower and instructions on how to perform the 4 hour surgery. As a result of my all too close encounter with the internal workings of the 87a, I've learned a few things, discovered a couple of errors in the instrutions provided me by Alpha, and helped rewrite them and include a photograph to illustrate how to replace the blower. The new blower worked perfectly, was far quieter, and, unlike the original, was in balance. And Then Problems Began....Silently Another four years later, however, I encountered a problem with the replacement blower Alpha had sent me. It stopped working. I finally noticed there was no air coming from the top of the case over the tubes. Major panic occurred. The amplifier was supposed to shut down if the tubes began to overheat. I turned off the amp as quickly as I could. 
I opened the case and didn't see anything wrong. I put the case back together, and opened the plate below the tube deck so I could see the blower, as seen in the photo at the right. I turned the 87a on - I saw the blower wasn't working, and immediately turned it off. I almost ordered a new blower as soon as I saw it not working, assuming it was bad. However, I decided to remove the blower once again - about a 4 hour job. When I had it out of the case, I plugged the blower (a 230 VAC device) into a 110VAC line, just to see if the motor would turn. (Use caution if you do this so you don't come in contact with 110 VAC.) It started spinning merrily along! The blower was NOT defective! That's when I noticed the wires were not properly installed in the blower's connector that plugs into its power supply. If you experience this problem, you need NOT pull the blower to repair the connector or test the blower to see if it works. Simply remove the transformer, and you can get to the connector for the blower to fix any improper attachment of the wires to the connector. That will save you lots of time. Ultimate Diagnosis The connector on the blower that plugs into the power supply was improperly assembled by the manufacturer. 
Rather than the wires being attached PROPERLY (as illustrated in the photo at left of the now repaired blower connector) so they depart the connector in the standard 90
degree manner, the manufacturer simply pushed them horizontally into the connector so they made light contact with the connector. Over time, this resulted in a failure of
the wires to stay in place on the connector and eventually vibrate loose.
The photo at right (although NOT the blower connector) illustrates how the manufacturer assembled the connector improperly by inserting the wires horizontally into the "top"
of the connector. The wires should have been rather pressed into the narrow "V" shaped slot on the end of the connector so they exit the connector at a 90 degree angle.
Done properly, the connector cuts through the insulation to make electrical contact and the wire is held in place by the clamping action of the end of the connector. Fault on Start Up Once I had the blower problem fixed, the case put on, and ready to go, I pressed the ON switch - and the 87a immediately faulted. I contacted Alpha Service, and received these instructions: - Leave the anodes disconnected and allow the amplifier to go past the 3 minute warm up. Let it set for 20 minutes. 
OK - that was easy. I followed their instructions, and - it worked! Nice to have the Alpha 87a fire up and sit there with the familiar, reassuring glow of the LEDs on the front
panel - and especially the sound - and look - of the blower running as it should. "Look", you ask? See the next paragraph for an explanation.
"Is the Blower Working" Modification 
I now have a small piece of string tied around one of the perforations in the top of the case over the tubes so I have a visual confirmation
that the blower is doing its job.
Blower QA Problems  The problem with my blower could have been caught at several opportunities: 1) Poor quality assurance on the manufacturer's part didn't catch it. The blower failed at some point, and, by having the optional muffin fan on the back of the 87a case as a precaution to cool the power supply, it masked the lack of noise from the blower. However, the muffin fan may have saved the expensive 3CX800A7 tubes from overheating. Blower Replacement Tips If you have a digital camera - take lots of pictures as you disassemble the 87a so you can follow them in reverse order to put it all back together. There are lots of little screws, bolts and nuts (some of varying lengths but otherwise identical) which MUST be used in particular locations to prevent contact with PC boards and other devices. Alpha mentions in their instructions that you may need a 90 degree screwdriver to do the blower replacement - you don't. I was able to remove and reassemble everything easily without one using screwdrivers of varying sizes. Poor Quality Control = Possible Tube Replacment 
The bottom line is that I am now looking for a set of backup 3CX800A7 tubes - a pricey problem all around which could have been prevented at several opportunities,
beginning with the manufacturer and supplier of the blower. Alpha could have inspected their supplier's products to ensure quality is enforced. I too could have caught it,
but didn't. I have to assume the 3CX800A7 tubes may have been subjected to heat stress, so I'm looking for a spare set as back up in case they fail.
Fuses Fuses were a big part of my trying to figure out what was wrong. There are the obvious two on the back of the case, there is the very visible "step-start" fuse, and then there's a sneaky little "cartridge" fuse that doesn't resemble what I would expect a fuse to look like. Alpha refers to this one as the "36V fuse" on the low voltage PC board, located toward the front of the cabinet and near the power transformer. Despite being called a 36V fuse, it is labeled as a 110VAC/2A fuse. 
This fuse resembles a small, clear glass cylinder, which is plugged into a raised white plastic socket near the top left corner of the vertically mounted low voltage PC board as you look from the rear of the case toward the front of the case. The fuse has two leads at one end of the cylinder, which plug into the socket. You can reach it (barely) with some needle nose pliers if you remove the nearby connector. Be VERY careful not to crush the glass cylinder with the pliers. You could also remove the power transformer to make it easier to get to the fuse. This unique fuse is available from Alpha for about $10. Disappointment? A Little...Sorta... I'll admit that I am a bit disappointed with the problems I've experienced with the Alpha 87a. However, keeping in mind that the 87a has given me so many hours of perfect operation, and the excellent technical support provided by Alpha when I encountered problems, the Alpha 87a is a great piece of equipment, and - you could almost say - a great investment. Alpha has released a new series of top of the line amplifiers - the Alpha 9500. With the significant increase in prices, I could almost sell my Alpha 87a today for the price I paid for it many years ago. The Pursuit of Excellence 
Despite how hard we try, there will always be failures - we need to learn from them to continue our pursuit of excellence. Competition will also press us to improve. Acom has an excellent line of linear amplifiers, including the auto-tune Acom 2000A - a worthy competitor to the Alpha 87a. I've shared the problems I've experienced with the folks at Alpha, including Molly, WØMOM, vice president of Alpha Radio Products, who has been very helpful in ensuring my problems have been resolved, and that future developments will be improved as a result. You can't ask for more! |