#Astron ss 25 service manual plus#
#Astron ss 25 service manual series#

If your supply has a compensation cap you will find it connected from pin 4 to pin 13 on the DIP package, or from pin 9 to pin 2 on the TO-5 round metal can. The 723 data sheet (which you can click on below) has a number of sample circuits, and some show no capacitor, some show 15pF, some show 100pF (also spec'd as 1 nF), and the largest is 500pF (5nF). The average Astron has NO compensation cap at all. Paul Webster VK2BZC elucidates: Power supply design with the LM723. One of the overlooked items is the compensation capacitor value - as this web page by Dr. I'veДЇound very few LMвЂ‘723 regulator circuit designs done really well. Problems resulting from poor 723 regulation circuit design shortcuts often rear their ugly head at much later dates.ДЄstrons circuit design engineer is certainly not the first, nor the last person to misunderstand or overlook certain characteristics of the LMвЂ‘723 regulator chip. Much of the mentioned data sheet information is often overlooked. Fortunately, the data sheet has all the required information. The 723 regulator chip is an excellent building block, but making one play well with multiple nearby 50kw (or higher) broadcast transmitters can be a test of ones engineering skills. The load impedance and current demand presented to the supply can be a big factor in its reliability. Many Astron power supplies work well for decades, a lot of the problems surface when feeding higher impedance and reactive loads.

Most of the crowbar problems I've seen (once past the Astron regulator board) were traced to older filter capacitors under relatively heavy loads. The crowbar circuit itself works well when triggered. The end result is often seen as erratic operation, false crowbar circuit firing and regulator chip failure. Proper 723 pre-regulation is another common circuit shortfall.

#Astron ss 25 service manual plus#

Plus there is poor response to high frequency glitches and noise. Said amps with a lot of open (and closed) loop gain makes a nice RF sniffer when the designer forgets to properly bypass various sections of the regulator circuit. There are on-chip amplifiers with an incredible amount of gain.

The 723 regulator is often placed in under engineered circuits. Many early Astron supply regulator boards are problematic. The common Astron linear supply is not a finished and reliable design, as this Three articles in the 'Linear power Supply Design and Theory' section below. The chip with one that is guaranteed below 32вЏ.Д«efore you start debugging your Astron, I suggest that you read the first Going to a mountaintop repeater site that gets cold in the winter I'd replace The LM723C is temperature derated - the performance is only guaranteed over aД вЊ to +70вЊ temperature range, instead of -55вЊ to +125вЊ. Note that the LM723C used by Astron is identical to the LM723 except that There is as true today as it was when the chip was introduced. Most of the chip reference sites have the data sheetДЄnd applications notes, and the theory and design information you will find

(originally designed and sold by Fairchild Semiconductor in the 1970s as the

#Astron ss 25 service manual series#

The linear Astron supplies are based on the common '723' series regulator chip In almost all cases you will want to add a fan blowing across the heatsink and a and a second one through the box (across the transformer and bridge rectifier) is definitely recommended (you will need to punch holes and add screening for that - and don't forget to ground the screening). My personal opinion, which a number of my repeater-building friends share, is that you never load any Astron at any more than 50%. In other words, the digits in the model number represent the peak intermittent current capacity.ДЇor example, an RS35 is rated by Astron for 35В amps peak, 25В amps continuous, but I have seen a number of them fail while driving continuous duty loads of 20 to 25 amps. This gives time for the heat sink (and pass transistors) to cool down. low current) a lot more than he talks (high current). Astron marketing gets around that by saying that in normal operation the user listens (i.e. Note that the Astron supplies are advertised with peak duty amperage numbers and in continuous duty can supply only about half of the rated current (that is, a twenty amp Astron can in reality supply only about ten amps continuously). You probably came to this web page because you have an Astron supply that has problems. Index of Astronв„ў Power Supply Information at Back to HomeД¬ompiled from a number of different sourcesД¬lick here or on the logo above to go to Astron's web site

Astron ss-25 service manual