GRiDCase 1520 DC-DC Converter Repair
While diagnosing a RAM failure in my more sickly GRiDCase 1520 I noticed an unpleasant odour coming from the rear of the machine. Pretty soon it started behaving erraticly, rebooting at random. It's capacitors again — this time in the DC-DC converter module. Time to break out the soldering iron!
Extracting the DC-DC converter requires opening up the computer. It was immediately obvious that at least one large capacitor had leaked: underneath the DC-DC converter a brownish liquid was pooling. It also coated the lower half of the converter PCB :-(
DC-DC Converter Overview
The DC-DC converter takes the DC input to the system (16.24V from battery/PSU bay or 9-20V from external barrel connector). It converts this to the various voltages required for the rest of the system.
There are multiple models for the GRiDCase 1500-series DC-DC Converter:
- LCD-115, GRiD part number 104144-00. Used with the two LCD display options. Provides −15, +5, and +12 DC outputs plus switchable 100VAC.
- PLASMA-116, GRiD part number 104145-00. Used with the two plasma display options. Provides −15, +5, +12, and +33V DC outputs.
The machine I'm repairing here had an LCD display.
![Back view of DC-DC converter](01-dcc-back.th.jpeg)
![Top view of DC-DC converter](02-dcc-top.th.jpeg)
![Front view of DC-DC converter](03-dcc-front.th.jpeg)
![Bottom view of DC-DC conveter](04-dcc-bottom.th.jpeg)
Removing the Capacitors
![Closeup of burst capacitor](05-badcap.th.jpeg)
![Cluster of leaking capacitors](06-badcap2.th.jpeg)
![Removed capacitors and insects](07-capsnbugs.th.jpeg)
![PCB after capacitor removal](08-caps-removed.th.jpeg)
The capacitors I removed and their values were:
Designator | Capacitance µF | Voltage V | Max Temp °C | Height mm | Diameter mm | Lead Spacing mm |
---|---|---|---|---|---|---|
C1 | 470 | 25 | 105 | 21 | 10 | 5 |
C19 | 2200 | 10 | 105 | 25 | 13 | 6 |
C20 | 220 | 16 | 105 | 12 | 5 | 5 |
C30 | 47 | 100 | 85 | 17 | 10 | 6 |
C31 | 47 | 100 | 85 | 17 | 10 | 6 |
C35 | 47 | 100 | 85 | 17 | 10 | 6 |
C61 | 1000 | 25 | 105 | 25 | 13 | 6 |
C71 | 47 | 50 | 85 | 12 | 6 | 3 |
C72 | 47 | 50 | 85 | 12 | 6 | 3 |
C73 | 3300 | 6.3 | 105 | 20 | 10 | 5 |
C74 | 470 | 6.3 | 105 | 12 | 10 | 5 |
C76 | 10 | 10 | 85 | 11 | 13 | 2 |
C80 | 1000 | 25 | 105 | 25 | 13 | 6 |
C81 | 1000 | 25 | 105 | 25 | 13 | 6 |
C82 | 3300 | 6.3 | 105 | 20 | 13 | 5 |
C83 | 3300 | 6.3 | 105 | 20 | 13 | 5 |
I managed to source replacements that met the capacitance; met or slightly exceeded the voltage and temperature rating; and were physically the same size or smaller.
Fitting Replacements
![PCB after cleaning](09-cleaned.th.jpeg)
![PCB with new capacitors fitted](10-new-caps-fitted.th.jpeg)
![Testing in place](11-testing.th.jpeg)