1987 Marshall JCM 800 2203

The 2203 is the quintessential JCM 800 made by Marshall and puts out an extremely loud 100 Watts of pure Metal. This 2203 was made in 1987 and has a few changes from the earlier JCM 800 models. The front panel has the updated horizontal input jacks rather than the vertical input jack arrangement previously used. This is just a superficial aesthetic change, but it signifies that Marshall had changed the construction within to use less hand-wiring and more importantly made a major alteration to the schematic design for the power supply. The change from vertical to horizontal input jacks (and construction styles) occurred around 1985, and was done in order to cut costs in an increasingly difficult market for products made in the USA and UK. For the 100 Watt models like the 2203 and 4103 Marshall reduced the number of electrolytic capacitor cans in the power supply resulting in much less filtering and therefore a noticeable change in sound quality. Critics say these amps do not hold up as well at high volumes and the general consensus is that they sound harsher, grainier, and lack the punch of the pre-1985 models. Tons of people love these later models however, and argue that they sound different but definitely not inferior. In fact a lot of the famous guitarists associated with the JCM 800 use these models exclusively. For many artists the brighter tone and less tight more raw sound at high volume is exactly what they like about the horizontal-input models. This change to the power supply however did not affect any of the 50 Watt models, like the 2204 or 4104. Notable users of the JCM 800 include: Ian Mackaye, Tom Morello, Slash, Larry LaLonde, Billy Corgan, Zack Wylde, and Kerry King.

This amp came in having been “repaired” about a month before, however the shop that worked on this just replaced the tubes and nothing else. Apparently they never bothered to look inside the chassis and see the caustic paste pushing out of all the exhaust ports on the electrolytic capacitor cans or that the screen resistors and some plate resistors were damaged by heat. There are other things they missed as well, but the fact that they let a nearly 40 year old amp out of the their shop without doing a basic cap job to a gigging musician is just ridiculous. Unsurprisingly this sounded like it was on the verge of lighting on fire and made a lot of noise but little music. I see this way too often in this town. It needed a cap job, new power/screen/plate resistors, one 12AX7 preamp tube, a new potentiometer, all new knobs, and cleaning.

The amp was given a full restoration. All the axial lead electrolytic capacitors were replaced with upgraded temperature rated Vishay brand electrolytics. The multi-section cap cans were replaced with new German made F&T 50/50uf 500v type units. The power dropping resistors were upgraded to 3 watt Metal Film type and the Screen Grid resistors were upgraded to 5 Watt Cement type units respectively. This was done for better noise floor and reliability from heat damage - the original units suffered from both of these issues.

1 ohm 2 Watt Metal Oxide resistors were installed on pin 8 of the power tubes to provide an easy way to check the bias. All plate resistors were replaced with 2 Watt Reduced Mass Metal Film type units for preventative maintenance and reliability - the originals were damaged by excess heat as well. The Presence pot was replaced with an Alpha brand 24mm Marshall style unit due to the original having a bent shaft. All new Marshall style knobs were put on as the original knobs were mismatched and did not physically fit the new pot.

The amp was already re-tubed - but the V3 preamp tube was shorted due to the malfunctioning filter caps. This was the final lineup: V1-V2 = RUBY 12AX7HG , V3 = EHX 12AX7, V4-V7 = SVETLANA EL34 Matched Quad. The adjustable Fixed Bias was set to %65 Class AB Plate Dissipation with a B+ of 465 VDC. The tube sockets were all treated with De-Oxit to remove/prevent corrosion. All pots were cleaned with De-Oxit and all hardware was tightened.