I recently completed a recap of an ASTEC power supply unit in my SE/30 and I thought I would share the particulars, in case any of you fellow tinkerers decide to do the same.
The reason I chose to recap is because I noticed the 5V line was running slightly low - around 4.85V - and tended to wobble a few hundredths of a volt during operations. I’m also troubleshooting a separate problem and wanted to rule out power supply issues. I looked around on the interwebs for guidance and found a little bit on the other site, but nothing recent. Since I have successfully recapped two Mac IIsi PSUs that were absolutely grungy, I decided to take the plunge and give it a go with the ASTEC PSU in my SE/30.
The hardest part was getting the darn PSU open and the wires with the plastic grommet detached. After a lot of finagling and bending of the case, I finally got it to release. The board is one-sided and soldered to the mains inputs, but I was able to flip the board and leave it soldered to do the desoldering work on the caps.
Hmm, I noticed a triplet of smaller safety caps on the primary side in a familiar gold color, one in the center and a pair near the ground wire in the lower right. Could those be RIFAs? Why yes, they sure are! I wonder if the reputation of ASTEC PSUs failing are due to RIFAs? I don’t know, but I decided to err on the side of caution and remove these.
I proceeded to remove al the caps on the secondary side. I opted to leave the large caps on the primary side in place. Sure enough, when I removed the cap at C35, I got a whiff of fishy smell. I believe I found my culprit.
Here is a family photo of the caps I removed. Several of the caps were glued to the board. I didn’t notice anything unusual about the color of the glue, just that there were copious amounts of it on some of the caps which made removal a bit of a bear, but I finally got them all.
I placed an order with Mouser for replacements. Here is what I ordered, for future reference;
Safety caps, X1/Y1
Secondary side caps
Most of the modern replacements are smaller in height than the originals, which helps with clearance around the heat shield.
Here is the PSU after recap complete and board fitted into the PSU case. The replacement blue ceramic safety caps on the primary side are visible, one in the center and two in the lower right near the ground wire. The replaced caps on the secondary side are hard to see, in the upper left of the photo and blocked by the transformer and heat shield. Also, the wires and plastic grommet required finagling again to get it into place, and you can probably tell that I resorted to bending the metal of the case to get it to fit into its original slot.
After that, it was time for a smoke test.
Success! Voltages are showing 12.1V and 5.00V and are rock steady. I’m happy with the outcome. The recap did not resolve the other problems I’m having (a topic for another thread someday), but at least I know it is not the PSU, and I took care of at least one obviously leaky cap and a triplet of RIFAs that were probably lying in wait to blow one of these days. My main reason for writing this is to share that as far as recaps go, this was fairly straight forward. Some of the dated material I found seemed to convey a sense of aversion to undertaking a recap like this, yet other than the frustration of finagling the plastic grommet and wires into and out of the PSU case, the repair was straight forward. Double and triple check the polarity of the replacement caps on the secondary side, check for RIFAs on the primary side, and I found it to be one of the easier PSU recaps I’ve done for about US $20 in parts and shipping.
Has anyone else tackled a recap of an SE/30 PSU? Let me know below. Thanks for reading!
The reason I chose to recap is because I noticed the 5V line was running slightly low - around 4.85V - and tended to wobble a few hundredths of a volt during operations. I’m also troubleshooting a separate problem and wanted to rule out power supply issues. I looked around on the interwebs for guidance and found a little bit on the other site, but nothing recent. Since I have successfully recapped two Mac IIsi PSUs that were absolutely grungy, I decided to take the plunge and give it a go with the ASTEC PSU in my SE/30.
The hardest part was getting the darn PSU open and the wires with the plastic grommet detached. After a lot of finagling and bending of the case, I finally got it to release. The board is one-sided and soldered to the mains inputs, but I was able to flip the board and leave it soldered to do the desoldering work on the caps.
Hmm, I noticed a triplet of smaller safety caps on the primary side in a familiar gold color, one in the center and a pair near the ground wire in the lower right. Could those be RIFAs? Why yes, they sure are! I wonder if the reputation of ASTEC PSUs failing are due to RIFAs? I don’t know, but I decided to err on the side of caution and remove these.
I proceeded to remove al the caps on the secondary side. I opted to leave the large caps on the primary side in place. Sure enough, when I removed the cap at C35, I got a whiff of fishy smell. I believe I found my culprit.
Here is a family photo of the caps I removed. Several of the caps were glued to the board. I didn’t notice anything unusual about the color of the glue, just that there were copious amounts of it on some of the caps which made removal a bit of a bear, but I finally got them all.
I placed an order with Mouser for replacements. Here is what I ordered, for future reference;
Safety caps, X1/Y1
| pF | VAC | lead spacing | Brand | Mouser | |
| C4 | 4700 | 250 | 10 | Murata | 81-DE1E3RA472MA4BN01F |
| C5 | 4700 | 250 | 10 | Murata | 81-DE1E3RA472MA4BN01F |
| C15 | 4700 | 250 | 10 | Murata | 81-DE1E3RA472MA4BN01F |
Secondary side caps
| uF | V | diameter | height | lead spacing | Brand | Mouser | |
| C32 | 47 | 25 | 6.3 | 11 | 2.5 | Vishay | 75-511D476M025AA4D |
| C36 | 1200 | 10 | 10 | 16 | 5 | Wurth | 710-860160275033 |
| C24 | 1200 | 10 | 10 | 16 | 5 | Wurth | 710-860160275033 |
| C35 | 470 | 16 | 8 | 11.5 | 3.5 | Wurth | 710-860010374012 |
| C23 | 470 | 16 | 8 | 11.5 | 3.5 | Wurth | 710-860010374012 |
| C28 | 220 | 16 | 8 | 11.5 | 3.5 | Wurth | 710-860240374006 |
| C19 | 220 | 25 | 8 | 11.5 | 3.5 | Wurth | 710-860040474004 |
| C21 | 47 | 63 | 8 | 11.512 | 3.5 | Wurth | 710-860040774002 |
Most of the modern replacements are smaller in height than the originals, which helps with clearance around the heat shield.
Here is the PSU after recap complete and board fitted into the PSU case. The replacement blue ceramic safety caps on the primary side are visible, one in the center and two in the lower right near the ground wire. The replaced caps on the secondary side are hard to see, in the upper left of the photo and blocked by the transformer and heat shield. Also, the wires and plastic grommet required finagling again to get it into place, and you can probably tell that I resorted to bending the metal of the case to get it to fit into its original slot.
After that, it was time for a smoke test.
Success! Voltages are showing 12.1V and 5.00V and are rock steady. I’m happy with the outcome. The recap did not resolve the other problems I’m having (a topic for another thread someday), but at least I know it is not the PSU, and I took care of at least one obviously leaky cap and a triplet of RIFAs that were probably lying in wait to blow one of these days. My main reason for writing this is to share that as far as recaps go, this was fairly straight forward. Some of the dated material I found seemed to convey a sense of aversion to undertaking a recap like this, yet other than the frustration of finagling the plastic grommet and wires into and out of the PSU case, the repair was straight forward. Double and triple check the polarity of the replacement caps on the secondary side, check for RIFAs on the primary side, and I found it to be one of the easier PSU recaps I’ve done for about US $20 in parts and shipping.
Has anyone else tackled a recap of an SE/30 PSU? Let me know below. Thanks for reading!
