Recap guide

Recap the Atari SM124, SM144, SC1224 and PCM124 monitors

The SM124 and SM144 are Atari ST monochrome monitors, the SC1224 is the ST colour monitor, and the PCM124 is the monitor made for Atari's PCs. The oldcrap.org lists give every capacitor, by board where the list splits them.

Open the interactive checklist Tick off each capacitor as you replace it. It saves in your browser.

Worth a recap. Reports say it is a common and useful fix on this machine.

Where to start

We did not find a clear list of what fails first on this machine, so we are not guessing. Read the guides below, check the board for leaks, and replace what you can see.

Before you start

• A monitor has a high-voltage tube and a power supply that can hold a charge long after you unplug it. If you are not trained to work on one, have a professional do it.
• Boards changed during production. Check your board number against the guides before you order parts.

SM124 monitor (29 parts)

From oldcrap.org's list for the Atari SM124 monochrome monitor, noted from the original parts. The list is one table with no board headings. C716 is bipolar.

SM144 main board (33 parts)

From oldcrap.org's list for the Atari SM144 monochrome monitor, noted from the original parts, under the heading Mainboard.

SM144 CRT board (4 parts)

From oldcrap.org's list, under the heading CRT Board.

SC1224 main board (55 parts)

From oldcrap.org's list for the Atari SC1224 colour monitor, noted from the original parts, under the heading Main Board. Three of the parts are bipolar (BP): C308, C318 and C328, which are 1 uF 50 V.

SC1224 CRT board (7 parts)

From oldcrap.org's list, under the heading CRT Board.

SC1224 power supply board (6 parts)

From oldcrap.org's list, under the heading Power Supply Board. C950 is a 400 V part, so unplug the monitor and let it drain.

PCM124 monitor (20 parts)

From oldcrap.org's list for the Atari PCM124 monitor, noted from the original parts. The list is one table with no board headings. C312 is bipolar and marked HF in the list.

Shopping list

154 capacitors in all, grouped by value. Buy a few spares.

• 14 x 22 µF, 16 V (check your board): Amazon · eBay
• 11 x 1 µF, 50 V (check your board): Amazon · eBay
• 10 x 10 µF, 16 V (check your board): Amazon · eBay
• 10 x 220 µF, 16 V (check your board): Amazon · eBay
• 8 x 1000 µF, 25 V (check your board): Amazon · eBay
• 7 x 47 µF, 16 V (check your board): Amazon · eBay
• 6 x 100 µF, 10 V (check your board): Amazon · eBay
• 5 x 1 µF, 160 V (check your board): Amazon · eBay
• 5 x 3.3 µF, 50 V (check your board): Amazon · eBay
• 5 x 100 µF, 16 V (check your board): Amazon · eBay
• 5 x 1000 µF, 16 V (check your board): Amazon · eBay
• 4 x 100 µF, 100 V (check your board): Amazon · eBay
• 4 x 330 µF, 16 V (check your board): Amazon · eBay
• 3 x 0.47 µF, 50 V (check your board): Amazon · eBay
• 3 x 2.2 µF, 50 V (check your board): Amazon · eBay
• 3 x 47 µF, 100 V (check your board): Amazon · eBay
• 3 x 100 µF, 25 V (check your board): Amazon · eBay
• 3 x 100 µF, 50 V (check your board): Amazon · eBay
• 3 x 120 µF, 400 V (check your board): Amazon · eBay
• 3 x 330 µF, 50 V (check your board): Amazon · eBay
• 3 x 2200 µF, 16 V (check your board): Amazon · eBay
• 2 x 4.7 µF, 50 V (check your board): Amazon · eBay
• 2 x 10 µF, 25 V (check your board): Amazon · eBay
• 2 x 10 µF, 160 V (check your board): Amazon · eBay
• 2 x 22 µF, 100 V (check your board): Amazon · eBay
• 2 x 47 µF, 10 V (check your board): Amazon · eBay
• 2 x 47 µF, 25 V (check your board): Amazon · eBay
• 2 x 100 µF, 160 V (check your board): Amazon · eBay
• 2 x 470 µF, 16 V (check your board): Amazon · eBay
• 2 x 1000 µF, 35 V (check your board): Amazon · eBay
• 1 x 0.1 µF, 50 V (check your board): Amazon · eBay
• 1 x 0.22 µF, 50 V (check your board): Amazon · eBay
• 1 x 1 µF, 100 V (check your board): Amazon · eBay
• 1 x 2.2 µF, 160 V (check your board): Amazon · eBay
• 1 x 8.2 µF, 50 V (check your board): Amazon · eBay
• 1 x 10 µF, 100 V (check your board): Amazon · eBay
• 1 x 10 µF, 50 V (check your board): Amazon · eBay
• 1 x 33 µF, 50 V (check your board): Amazon · eBay
• 1 x 33 µF, 16 V (check your board): Amazon · eBay
• 1 x 33 µF, 160 V (check your board): Amazon · eBay
• 1 x 47 µF, 50 V (check your board): Amazon · eBay
• 1 x 220 µF, 25 V (check your board): Amazon · eBay
• 1 x 220 µF, 160 V (check your board): Amazon · eBay
• 1 x 330 µF, 25 V (check your board): Amazon · eBay
• 1 x 470 µF, 50 V (check your board): Amazon · eBay
• 1 x 2200 µF, 35 V (check your board): Amazon · eBay
• 1 x 2200 µF, 10 V (check your board): Amazon · eBay
• 1 x 3300 µF, 35 V (check your board): Amazon · eBay

Skip the sourcing

• Ready-made kit: Amazon · eBay
• Already recapped: Amazon · eBay

While you are in there

• Need the machine itself?: Amazon · eBay
• A box of spare capacitors: Amazon · eBay

Affiliate links. As an Amazon Associate I earn from qualifying purchases. These links only search by name. Disclosure

Step by step

1. Photograph both sides of the board before you touch anything. Zoom in on every capacitor. The photo is your map when you are three hours in.
2. Unplug it, take out the batteries and let it sit. Old power supplies and CRT parts can hold a charge. If your machine has a tube, leave the tube and its board to a professional.
3. Open it up and keep the screws sorted. A muffin tin or an egg carton works. Different screws go in different holes, and the holes never forgive you.
4. Look for leaks. Clean any sticky residue off with isopropyl alcohol and a soft brush. A leaked capacitor leaves brown crust and can eat copper traces. Look at the traces under it, not only the part itself.
5. Mark the polarity of every capacitor on the photo before it comes off. On an electrolytic, the stripe marks the negative leg. The board usually shows a half-shaded circle or a bar for the same spot.
6. Remove the old capacitors one at a time. Surface mount: add fresh solder to both ends and rock the part off, or use flux and a low-melt alloy. Through-hole: heat one leg at a time and clear the hole with wick or a pump.
7. Clean the pads and check for lifted pads or damaged traces. Clean flux off with isopropyl. A bad pad needs a jumper wire, not hope.
8. Fit and solder the new capacitor, matching polarity. Same capacity, same or higher voltage, and it has to physically fit. Work from the smallest parts up.
9. Clean the flux off and look at every joint. A good joint is shiny and shaped like a tiny volcano. A dull blob or a ball is a cold joint: reflow it.
10. With a multimeter, check for shorts across the power rails before you power it on. Use the continuity or resistance setting. A reading near zero means stop and look for a solder bridge.
11. Power it up and test everything: video, sound, controls, the lot. If something is wrong, check polarity first. It is the most common mistake and the easiest fix.

Tools

• Temperature-controlled soldering station. Steady heat so you do not cook pads. Most recaps are done between 320 and 350 C. Top: Hakko FX-951 · Mid: Hakko FX-888D · Budget: Pinecil
• Good solder. Rosin-core 63/37 flows and looks right. It is cheap and it matters. Kester 44 63/37
• Flux. Flux is what makes old joints let go and new joints flow. MG Chemicals flux pen · Chip Quik flux syringe
• Low-melt alloy (for surface mount). Melts old solder on both ends of a surface mount part at once, so it lifts off cleanly. Chip Quik SMD1
• Desoldering tool. Clears the old solder out of through-hole pads. Top: Hakko FR-301 · Mid: Engineer SS-02 pump · Budget: Solder wick
• Fine tweezers. For holding small surface mount parts exactly where you want them. ESD-safe tweezers
• Board holder. A third hand for the board, so both of yours are free. PanaVise circuit board holder
• Magnification. You cannot fix what you cannot see. Surface mount parts are tiny. Top: Stereo microscope · Mid: Head visor · Budget: Lighted magnifier
• Multimeter. Continuity, shorts and rail voltages. The one test that saves boards. Top: Fluke 117 · Mid: Fluke 101 · Budget: AstroAI
• ESR and capacitor tester. Checks old capacitors and your new ones before they go in. Top: Peak Atlas ESR70 · Budget: LCR-T7
• Isopropyl alcohol (99%) and a brush. For cleaning leaked goo and flux. Use the high-percentage kind. MG Chemicals 99.9% isopropyl
• Brass tip cleaner. A clean tip transfers heat. A dirty one does not. Hakko 599B
• Fume extractor. Pulls the smoke away from your face. Hakko FA-400 · Budget: Small bench fan
• Precision screwdrivers. Most old gear uses a mix of Phillips, Torx and security bits. iFixit Pro Tech Toolkit
• Kapton tape. Heat-proof tape to protect parts that sit close to the one you are changing. Kapton tape

Safety

• Good airflow, or a fume fan. Solder smoke is not for breathing.
• Safety glasses on. Solder spits and clipped legs fly.
• Iron in its stand when you are not holding it. Know where the cord is.
• Touch bare metal first, or use a wrist strap. Static kills old chips.
• No tube, no mains power supply. Leave those to a professional.
• Wash your hands after, especially if you used leaded solder.

Values are shown as published in the guides above, and boards changed during production. Check the board in front of you. A recap involves hot tools and, on some machines, dangerous voltages. You do it at your own risk.

More

• All recap guides
• The interactive Recap Bench
• Fix a dead vintage computer
• Atari SM124 on the timeline
• Atari SC1224 on the timeline
• Atari SM144 on the timeline
• Atari PCM124 on the timeline