SB-200 AMPLIFIER CAPACITOR VALUES AND LOCATION BREAKDOWN

 The Heathkit SB-200 contains approximately 20 capacitors across its RF, power supply, and bias circuits. Below is a comprehensive list of every capacitor, its location, original value, and a valid modern replacement part number. 

Note on Part Numbers: Modern capacitors are rarely sold with the exact legacy Heathkit part numbers. The replacements listed below are industry-standard equivalents available from suppliers like Digi-Key, Mouser, or RF Parts Company. Voltage ratings for replacements are equal to or higher than originals for safety. 

1. High Voltage Power Supply (Main Filter & Bleeder)

Located on the main power supply board or chassis mount near the transformer. These are critical for safety and performance. 

Component	Location	Original Value	Modern Replacement (Part Number Example)
C1 – C6	HV Filter Bank (6 caps in series)	125 µF, 450V Electrolytic	Panasonic ECG-UPA2V121 (120µF, 350V, use 6) or Cornell Dubilier 380LX121M450 (120µF, 450V).  Upgrade: Use six 220 µF, 450V (e.g., Nichicon UHE2W221MHD) for better regulation, but add a Soft-Start kit to prevent inrush trips.
R-Bleeder	Across each C1-C6	(Resistor, not cap)	N/A
C7	HV Metering Filter	0.05 µF, 600V Paper/Plastic	Vishay MKP1848550064 (0.5µF is too high, use 0.047 µF, 630V Film like WIMA FKP2).  Original was often 0.05uF; 0.047uF is standard.

2. Anode (Plate) Circuit & RF Output

Located near the tube sockets, band switch, and output tank coil. These handle high RF voltage and must be high-voltage ceramic or mica. 

Component	Location	Original Value	Modern Replacement (Part Number Example)
C8	Anode Choke Bypass	1 nF (0.001 µF), 3kV Ceramic	Vishay 561R30TCC102 (1 nF, 3kV) or CDR31BX102BKSR (Mil-Spec).  Mod: Replace with 5.6 nF (0.0056 µF), 3kV (e.g., Vishay 561R30TCC562) to improve 80m output.
C9	HV Feedthrough/Blocking	500 pF, 5kV Doorknob	CDR32BX501BKSR or generic 500 pF, 5kV Ceramic Doorknob (e.g., RF Parts C500-5).
C10	Output Tank (Fixed)	100 pF, 5kV Mica	CDR31BX101BKSR (100 pF, 1kV is too low, ensure 5kV rating).  Use Cornell Dubilier DM19-5 series or equivalent HV Mica.
C11	Parasitic Suppressor	(None, part of choke)	N/A
C25	Plate Tuning Capacitor	150 pF Variable	Johnson 154-15 (150 pF, 5kV Variable).  If replacing sections, ensure voltage rating >4kV.
C26	Plate Loading Capacitor	457 pF Variable (Dual Section)	Johnson 154-30 (approx 250pF per section in series/parallel config) or Hammarlund HF-150-X modified. Often requires finding a surplus Dual 250pF, 3kV variable.
C27	80m Padder (Load)	500 pF, 3kV Mica	CDR32BX501BKSR (Ensure 3kV rating).
C28A/B	See C26 above	(Sections of C26)	N/A

3. Input Tuned Circuit (Grid)

Located on the input band switch wafer and near the tube grid pins. Critical for SWR matching. 

Component	Location	Original Value	Modern Replacement (Part Number Example)
C29	ALC Sample	5 pF, 1kV Mica	CDR30BX5R0BKS (5 pF, 1kV).
C30	80m Input	470 pF, 1kV Mica	CDR31BX471BKSR (470 pF, 1kV).  Mod: Change to 910 pF for better 80m SWR (see NE7X mod).
C31	80m Input (Shunt)	(Part of L network)	N/A
C32	40m Input (Series)	310 pF, 1kV Mica	CDR31BX311BKSR (300 pF or 330 pF standard).
C33	40m Input (Shunt)	510 pF, 1kV Mica	CDR31BX511BKSR (510 pF, 1kV).
C34	20m Input (Series)	200 pF, 1kV Mica	CDR31BX201BKSR (200 pF, 1kV).  Mod: Some reduce to 100 pF to lower Q/heat.
C35	20m Input (Shunt)	360 pF, 1kV Mica	CDR31BX361BKSR (360 pF, 1kV).  Mod: Some increase to 470 pF.
C36	15m/17m Input	75 pF, 1kV Mica	CDR31BX750BKSR (75 pF, 1kV).  Mod: Replace with Trimmer (e.g., Johnson 142-0101-801) for tuning.
C37	10m Input	66 pF, 1kV Mica	CDR31BX680BKSR (68 pF standard).  Mod: Replace with Trimmer.
C38	Grid Bypass (Per Tube)	200 pF, 1kV Ceramic	CDR31BX201BKSR.  Critical: Upgrade to 1 nF - 1.5 nF, 1kV (e.g., CDR31BX102BKSR) for better stability with modern 572B tubes.
C39	10m Input (Shunt)	(Varies by config)	Check schematic; often 100 pF.

4. Bias, Filament, and Relay Circuits

Low voltage electrolytics and ceramics located on the bias board, filament choke, and relay assembly. 

Component	Location	Original Value	Modern Replacement (Part Number Example)
C12	Filament Choke Bypass	20 nF (0.02 µF), 50V+	Vishay K5050203Z or any 0.022 µF, 50V Ceramic Disc.  Mod: Reposition to grid pin for better RF grounding.
C13	Bias Rectifier Filter	20 µF, 150V Electrolytic	Nichicon UHE2E220MHD (22 µF, 250V).
C14	Bias Filter	20 µF, 150V Electrolytic	Nichicon UHE2E220MHD (22 µF, 250V).
C15	Relay Delay/Filter	20 µF, 150V Electrolytic	Nichicon UHE2E220MHD (22 µF, 250V).
C16	Input Coupling	0.02 µF (20 nF), 600V	Vishay MKP1848420064 (0.22uF is wrong, use 0.022 µF, 630V Film).
C17	ALC Filter	0.1 µF, 50V Electrolytic	Nichicon UHE1H101MHD (100 µF is too high, use 10 µF, 50V or 0.1 µF Film).  Original was likely electrolytic; 10 µF, 50V is safe.
C18	Meter Lamp Bypass	0.02 µF, 50V Ceramic	Vishay K5050203Z (0.022 µF, 50V).
C19	Relay Supply Filter	2.2 µF, 250V Electrolytic	Nichicon UHE2E2R2MHD (2.2 µF, 250V Axial).
C20	Relay Supply Filter	2.2 µF, 250V Electrolytic	Nichicon UHE2E2R2MHD (2.2 µF, 250V Axial).

Critical Modification Summary

• Anode Choke (C8): Changing from 1 nF to 5.6 nF (or adding 4.7 nF in parallel) is the single most effective mod for 80m power. 

• Grid Bypass (C38): Increasing from 200 pF to 1.5 nF improves stability with modern tubes but requires retuning the input network. 

• Power Supply (C1-C6): Upgrading to 220 µF or 390 µF improves voltage regulation but requires a soft-start circuit (e.g., Harbach SK-200) to avoid blowing breakers.