Schematics

Loud has a selection of schematics, manuals, and literature available for their discontinued products in their Technical Support Library. The link to the library is available here: Ampeg : Support.

Vintage Blue Document Collection: the definitive source for redrawn Ampeg Portaflex and Oliver schematics and service manuals.

Vintage Blue Document Collection​

Ampeg​

A15/B15 Schematic (6/60) PDF JPG

B15N Schematic (March 1961) PDF JPG

B15NA Schematic, Version 1 PDF JPG

B15NA Schematic, Version 2 PDF JPG

B15NB Schematic PDF JPG

B15NB Service Manual PDF

B15NC Schematic (1/64) PDF JPG

B15NC Schematic (4/64) PDF JPG

B15NC Schematic (9/64) PDF JPG

B15NC Schematic (11/64) PDF JPG

B15NC Schematic (1/65) PDF JPG

B15NC Schematic (2/65) PDF JPG

B15NC Schematic (3/65) PDF JPG

B15NF Schematic (4/65) PDF JPG

B15NF Schematic (9/65) PDF JPG

B15NF Schematic (1/66) PDF JPG

B15NF Service Manual (circa '67/'68) PDF



B18N Schematic (SSR) PDF JPG

B18N Service Manual PDF

B18N Schematic (1/65) PDF JPG

B18N Schematic (1/66) PDF JPG

B18N/B15ND Schematic (10/66) PDF JPG

B18N/B15ND Schematic (5/67) PDF JPG



B12X Schematic Version 1 PDF JPG

B12X Schematic Version 2 (from service manual) PDF JPG

B12X Service Manual PDF

B12XT B18X Service Manual PDF


SB-12 Schematic (10/65) PDF JPG

SB-12 Schematic (5/66) PDF JPG

SB-12 Schematic (6L6 ver.) circa '67-'68 PDF JPG


Portaflex XLR-to-¼" adapter cables PDF JPG


Portaflex XLR Extension Cables PDF JPG

Oliver Amp Company​

B-120 Schematic PDF JPG

B-122 Schematic PDF JPG

G150R/G200R Schematic PDF JPG

OP-1/OP-2 Orbital Power Projector Schematic PDF JPG

PA100X PDF JPG

PA100XR PDF [JPG]

Powerflex P502 Schematic PDF JPG

Powerflex P500/P502 Cabinet Wiring 1 PDF JPG

Powerflex P500/P502 Cabinet Wiring 2 PDF JPG

B15-NA​

B-15NA Version 1 Schematic

B-15NA Version 2 Schematic

B-15NA Original Schematic

B-15NB​

B-15NB Schematic

B-15NB Service Manual

B15-NC​

B-15NC Schematic 1-64

B-15NC Schematic 9-64

B-15NC Schematic 11-64

B-15NC Schematic 1-65

B-15NC Schematic 2-65

B-15NC Schematic 3-65

B-15ND​

Same schematic as B-18N.


B-18N B-15ND Schematic 10-66

B-18N B-15ND schematic 5-67

B-18N Service Manual

B15-NF​

B-15NF Schematic 4-65

B-15NF Schematic 9-65

B-15NF Schematic 1-66

B-15NF Service Manual

B-15N (1968-1980)​

B-15NF 1968 Schematic

B-15S​

B-15S 12-71 Schematic

B-15S Rev C Schematic

SB-12​

A description of the 7868 based SB-12 circuits and how they function can be found in the article "Totally Tubular! Get Behind that Titanic Tube Tone" by Jonathan Herrera, Bass Player, July 2008, Vol. 19 Issue 7, p41-53.


SB-12 7868 1966 Schematic

SB-12 6L6GC Schematic

SB-12 6L6GC II Schematic

SB-12 Owner's Manual 1967

SB-12 Owner's Manual II

Totally Tubular! by Jonathan Herrera, Bass Player article describing the SB-12 circuit

B-18N​

The B-18N, came with either a 8 or 16 ohm speaker. The Fane speaker was 16 ohms, the Cleveland was 8 ohms. But other speakers were used as well. The same Output transformer was used but it was wired differently.

With the 8 ohm version, when you plugged in an 8 ohm extension cabinet, the two 8 ohm speakers were connected in Series and switched to the 16 ohm transformer tap. With the 16 ohm version, when you plugged in a 16 ohm extension cabinet, the two 16 ohm speakers were connected in Parallel and switched to the 8 ohm transformer tap. Any other combination and you will have an impedance mismatch so care must be taken when connecting an external speaker cabinet to make sure that you have the correct one.

The only way to know if your amp is wired for 8 or 16 ohms is to check the wiring in the chassis and compare it to the schematic. The Output transformer secondary color code is green - 16 ohms, yellow - 8 ohms, and black - 0 ohms or ground. The ext speaker jacks are different, the 8 ohm jack has a single shunt normally closed switch. The 16 ohm jack has two switches, one normally Open, one normally closed. This acts the same as the the ext spkr jack used in the early SVT amps.

You can determine if you have an 8 or 16 ohm speaker by measuring the DC resistance with an ohm meter. Disconnect the speaker from the amplifier first and measure the resistance across the speaker terminals. The DC resistance will average about 70% the nominal resistance. The nominal resistance is the resistance indicated on the speaker label. Not all speakers have a label in place. An 8 ohm speaker will average around 5.6 ohms, a 16 ohm speaker will measure around 11.2 ohms. It is always a good idea to measure that resistance of the speaker just to be sure, despite what the label indicates. Sometimes the wrong label is in place or the speaker may have been reconed with a coil that is a different impedance.

ref:[1]

B-18N 1-66 16 ohm Schematic

B-18N Solid State Rectifier Schematic

B-18N B-15ND 5-67 Schematic

B-18N User's Manual

B-18X​

Same schematic as the B12XT.

B-12XT B-18X 5-67 Schematic

B-12​

Many of the B15 and B12 amps shared the same amplifier. The speaker cabinets differed. These B-12's had a different amplifier.

B-12XY​

B-12XY Schematic

B-12XT​

B-12XT 1-67 Schematic

B-12XT B-18X 5-67 Schematic

B-12X​

B-12X Schematic

B-12X Service Manual

BT-15​

BT-15 Manual

BT-15C Manual

BT-15D Manual




BT-15 BT-15C BT-15D BT-18C Schematic

BT-15 Schematic 1

BT-15 Schematic 2

BT-15 1B Schematic

BT-15-18 Schematic

B-15R​

B15R Schematic 26701H4

B15R Crossover 72961P0

B15R Goop 26701P4

B15R CSB0004

B-15T​

B15T Schematic

B15T Biasing Information

B15T Literature

Pre-Portaflex Amplifiers​

Amps such as the 600 and 800 Series have a lot in common with the Portaflex amps. Schematics for several revisions are available in this page's Attachments directory.


435S - 635S

625D Schematic 1

625D Schematic 2

625D Schematic 3

625D Schematic 4

625D Schematic 5

835 Schematic

835N Schematics 1

835N Schematics 2

Ampeg Preamp (1940) Schematic

Upright Electronic Bass BB4 and BB5​

Upright Bass BB4 and BB5