Ampeg SVT CSB0003 Schematic

SLM Electronics		#CSB0003
A Division of St. Louis Music, Inc
11880 Borman Dr		Service Department
St. Louis, MO 63146		Phone [phone]
Phone [phone]		Fax [phone]
November 6, 1997	Customer Service Bulletin

Units Affected:

SVT-2PROJ units serial numbered T2PJJ40001 through T2PJJ40042

SVT-2PROJ units serial numbered T2PJJ80001 through T2PJJ80010

SVT-CLJ units serial numbered TCLJJ40001 through TCLJJ40032

SVT-CLJ units serial numbered TCLJJ60001 through TCLJJ60002

SVT-CLJ units serial numbered TCLJJ90001 through TCLJJ90020

Note: A number of units in these serial number ranges have been factory modified to correct the problem. These units do not need to be modified in the field. They can be identified by the presence of a “Star Quality” label affixed to the outside of the shipping carton adjacent to the serial number/Bar code label.

Concern:

AC mains fuse for filament transformer would fail prematurely during normal operation when turning unit on as a result of a design change to use IEC approved fuse beginning with 1/1/97 production. Replacement with larger value fuse would solve false tripping problem but would not always provide adequate protection against damage duringsevere fault condition.

Corrective Action:

Add two each 3A in-rush current limiters (ICL’s) that have been prepared with .187” Fast-on connectors (SLME part number 97-123-23) to the filament transformer primary circuit as follows:

1.Disconnect the AC power from the unit.

2.Remove lower chassis assembly from cabinet and view from bottom.

3.On the 07-319-xx AC termination PC board, remove blue and gray leads from tabs J17 and J18.

4.Add one 97-123-23 ICL assembly in series with the blue transformer lead and tab J17, and one in series with the gray lead and J18 by attaching the female Fast-on connector of ICL to the tab on the printed circuit board and the male Fast-on to transformer lead.

5.Secure the assembly with a cable tie to other AC wires so that no leads are touching other parts.

6.Replace the fuse (F2) with a T1.25A (SLME part number 23-512-05).

7.Remove any fuse label so that “100VAC T1.25A” is visible on the printed circuit board.

8.Reassemble and check out unit for proper operation.

Note: For best operation of ICLs do not rapidly turn the amplifier off and on. These devices are selfheating and require a short time to cool and return to their protective, “high resistance” state.

07-319-xx AC Termination board as viewed from inside lower chassis

Add one 97-123-23 ICL assembly in series with J17 and the blue transformer lead and one in series with J18 and the gray transformer lead.